{"id":75809,"date":"2024-07-03T17:40:38","date_gmt":"2024-07-03T12:10:38","guid":{"rendered":"http:\/\/198.58.113.91\/blog\/?p=75809"},"modified":"2024-07-04T00:53:22","modified_gmt":"2024-07-03T19:23:22","slug":"mbr2gpt-cannot-find-os-partition","status":"publish","type":"post","link":"https:\/\/www.winhelponline.com\/blog\/mbr2gpt-cannot-find-os-partition\/","title":{"rendered":"MBR2GPT | Cannot find OS partition(s)"},"content":{"rendered":"

MBR2GPT.EXE is a built-in console tool that converts a disk from the Master Boot Record (MBR) to the GUID Partition Table (GPT) partition style without modifying or deleting data on the disk.<\/p>\n

When you run MBR2GPT to validate the disk before converting it to GPT, the following error may occur:<\/p>\n

Cannot find OS partition(s) for disk 0<\/pre>\n
<\/p>\n
\"mbr2gpt-<\/p>\n
RELATED:<\/strong> How to Find if a Disk Uses MBR or GPT<\/a><\/div>\n
Cause<\/h2>\n
There may be multiple reasons for the error “Cannot find OS partition(s) for disk #,” but incorrect entries in the Boot Configuration Database is the usual cause. Another reason is that the system may have booted in UEFI mode (even though the disk is MBR), and “BCD” doesn’t exist in the MBR boot path — i.e., \\Boot\\BCD<\/code>.<\/p>\n
The BCD may have entries pointing to a non-existent device. Or, the BCD file may be missing from the \\Boot\\BCD<\/strong><\/code> folder because the system uses the UEFI boot path — \\EFI\\Microsoft\\Boot<\/strong><\/code>.<\/p>\n
You can verify the boot mode using the System Information tool (msinfo32.exe). Check the “BIOS mode” setting on the System Summary page in msinfo32.exe. It shows “UEFI” if the system has booted in UEFI mode or “BIOS” for legacy boot.<\/div>\n
RELATED:<\/strong> MBR2GPT | Too many MBR partitions found, no room to create EFI system partition<\/a><\/div>\n
Resolution<\/h2>\n
To resolve the error “Cannot find OS partition(s) for disk #,” follow these steps:<\/p>\n
First, rebuild the BCD. To do so, run the following commands from an admin Command Prompt.<\/p>\n
bcdboot C:\\Windows \/s C: \/f ALL<\/pre>\n
If the above command runs successfully, open Disk Management and set the C drive and the active partition if it’s not already the active partition. To do so, right-click the C drive and choose “Mark partition as active<\/strong>.”<\/p>\n
\"mbr2gpt-<\/p>\n
\n
Note:<\/strong><\/p>\n
After marking the C drive as the active partition, you can optionally delete the System Reserved partition (if you have one) using diskpart<\/em>\u00a0after a reboot.<\/p>\n
\n
Next, access your BIOS settings and enable “Legacy” boot mode.<\/p>\n
Then, validate and convert the disk to GPT using MBR2GPT. Once booted into Windows using legacy mode, run MBR2GPT and validate the disk to see if any errors are reported. To do so, use this syntax:<\/p>\n
Syntax:<\/strong><\/p>\n
MBR2GPT \/validate [\/disk:<diskNumber>] [\/allowFullOS]<\/pre>\n
Example:<\/strong><\/p>\n
MBR2GPT \/validate \/allowfullos<\/pre>\n
(If the disk number is not specified, the system disk is used.)<\/em><\/p>\n
Disk validation using MBR2GPT should now run successfully.<\/p>\n
\"mbr2gpt-<\/p>\n
Now, convert the disk to GPT using the following command:<\/p>\n
MBR2GPT \/convert \/allowfullos<\/pre>\n
\"mbr2gpt-<\/p>\n
It should show the message “MBR2GPT: Conversion completed successfully” on the output screen.<\/p>\n
MBR2GPT will now attempt to convert disk 0.\nIf conversion is successful the disk can only be booted in GPT mode.\nThese changes cannot be undone!\n\nMBR2GPT: Attempting to convert disk 0\nMBR2GPT: Retrieving layout of disk\nMBR2GPT: Validating layout, disk sector size is: 512 bytes\nMBR2GPT: Trying to shrink the OS partition\nMBR2GPT: Creating the EFI system partition\nMBR2GPT: Installing the new boot files\nMBR2GPT: Performing the layout conversion\nMBR2GPT: Migrating default boot entry\nMBR2GPT: Adding recovery boot entry\nMBR2GPT: Fixing drive letter mapping\nMBR2GPT: Conversion completed successfully<\/strong>\nCall WinReReapir to repair WinRE\nMBR2GPT: Failed to update ReAgent.xml, please try to  manually disable and enable WinRE.\nMBR2GPT: Before the new system can boot properly you need to switch the firmware to boot to UEFI mode!\n<\/pre>\n
Now, switch to “UEFI” or “UEFI only” mode in the BIOS and boot into Windows. That’s it.<\/p>\n
\"UEFI-only<\/p>\n
\n
RELATED:<\/strong> MBR2GPT – Windows Deployment | Microsoft Learn<\/a><\/div>\n
Note:<\/strong><\/p>\n
If the bcdboot<\/strong><\/code> command mentioned above doesn’t fix the issue, analyze the C:\\Windows\\Setupact.log<\/code> file. In some cases, you need to boot into WinRE, rename \\Boot\\BCD<\/code>, and then run the bootrec \/rebuildbcd<\/strong><\/code> command to regenerate a new BCD.<\/p>\n","protected":false},"excerpt":{"rendered":"
MBR2GPT.EXE is a built-in console tool that converts a disk from the Master Boot Record (MBR) to the GUID Partition Table (GPT) partition style without modifying or deleting data on the disk. When you run MBR2GPT to validate the disk before converting it to GPT, the following error may occur: Cannot find OS partition(s) for … Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[8],"tags":[191],"class_list":["post-75809","post","type-post","status-publish","format-standard","hentry","category-windows-10","tag-error-messages"],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack-related-posts":[{"id":75476,"url":"https:\/\/www.winhelponline.com\/blog\/mbr2gpt-too-many-mbr-partitions\/","url_meta":{"origin":75809,"position":0},"title":"MBR2GPT | Too many MBR partitions found, no room to create EFI system partition","author":"Ramesh","date":"June 10, 2024","format":false,"excerpt":"When you convert your MBR disk to GPT using MBR2GPT, the error \"Too many MBR partitions found\" may occur. Here's the relevant info from the log: Error ValidateLayout: Too many MBR partitions found, no room to create EFI system partition. Error Disk layout validation failed for disk 2 This error\u2026","rel":"","context":"In "Windows 10"","block_context":{"text":"Windows 10","link":"https:\/\/www.winhelponline.com\/blog\/category\/microsoft\/windows\/windows-10\/"},"img":{"alt_text":"mbr2gpt - too many MBR partitions","src":"https:\/\/i0.wp.com\/www.winhelponline.com\/blog\/wp-content\/uploads\/2024\/06\/diskmgmt-mbr2gpt-error.jpeg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.winhelponline.com\/blog\/wp-content\/uploads\/2024\/06\/diskmgmt-mbr2gpt-error.jpeg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/www.winhelponline.com\/blog\/wp-content\/uploads\/2024\/06\/diskmgmt-mbr2gpt-error.jpeg?resize=525%2C300&ssl=1 1.5x, https:\/\/i0.wp.com\/www.winhelponline.com\/blog\/wp-content\/uploads\/2024\/06\/diskmgmt-mbr2gpt-error.jpeg?resize=700%2C400&ssl=1 2x, https:\/\/i0.wp.com\/www.winhelponline.com\/blog\/wp-content\/uploads\/2024\/06\/diskmgmt-mbr2gpt-error.jpeg?resize=1050%2C600&ssl=1 3x"},"classes":[]},{"id":57345,"url":"https:\/\/www.winhelponline.com\/blog\/find-if-disk-is-mbr-or-gpt\/","url_meta":{"origin":75809,"position":1},"title":"How to Find if a Disk Uses MBR or GPT","author":"Ramesh","date":"July 1, 2023","format":false,"excerpt":"Knowing how your disks were set up (MBR vs. GPT) is essential for troubleshooting boot issues and Windows Update errors. Master Boot Record (MBR) disks use the standard BIOS partition table. GUID partition table (GPT) disks use the Unified Extensible Firmware Interface (UEFI). The boot files reside in the System\u2026","rel":"","context":"In "Windows 10"","block_context":{"text":"Windows 10","link":"https:\/\/www.winhelponline.com\/blog\/category\/microsoft\/windows\/windows-10\/"},"img":{"alt_text":"diskpart gpt disk or mbr","src":"https:\/\/i0.wp.com\/www.winhelponline.com\/blog\/wp-content\/uploads\/2023\/07\/diskpart-mbr-disk.png?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.winhelponline.com\/blog\/wp-content\/uploads\/2023\/07\/diskpart-mbr-disk.png?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/www.winhelponline.com\/blog\/wp-content\/uploads\/2023\/07\/diskpart-mbr-disk.png?resize=525%2C300&ssl=1 1.5x, https:\/\/i0.wp.com\/www.winhelponline.com\/blog\/wp-content\/uploads\/2023\/07\/diskpart-mbr-disk.png?resize=700%2C400&ssl=1 2x"},"classes":[]},{"id":74912,"url":"https:\/\/www.winhelponline.com\/blog\/bootrec-fixboot-access-is-denied\/","url_meta":{"origin":75809,"position":2},"title":"Error “Access is Denied” when running “Bootrec \/Fixboot”","author":"Ramesh","date":"April 23, 2024","format":false,"excerpt":"When you run the \"bootrec \/fixboot\" command from Windows RE, the error \"Access is denied\" occurs: Bootrec \/FixMbr -- writes the master boot record of the system partition using the master boot record compatible with Windows. This operation does not overwrite the existing partition table. Bootrec \/FixBoot -- write a\u2026","rel":"","context":"In "Windows 10"","block_context":{"text":"Windows 10","link":"https:\/\/www.winhelponline.com\/blog\/category\/microsoft\/windows\/windows-10\/"},"img":{"alt_text":"bootrec \/fixboot access denied","src":"https:\/\/i0.wp.com\/www.winhelponline.com\/blog\/wp-content\/uploads\/2024\/04\/fixboot-access-denied-gpt-uefi.png?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":75024,"url":"https:\/\/www.winhelponline.com\/blog\/windows-cant-install-gpt-partition\/","url_meta":{"origin":75809,"position":3},"title":"Windows cannot be installed to this disk. The selected disk is of the GPT partition style","author":"Ramesh","date":"May 1, 2024","format":false,"excerpt":"When you clean install Windows 10 or 11 on your computer by booting from the USB setup disk, the following notification may be displayed: Windows can't be installed on drive n partition n When you click on the above notification, the following error message appears: Windows cannot be installed to\u2026","rel":"","context":"In "Windows 10"","block_context":{"text":"Windows 10","link":"https:\/\/www.winhelponline.com\/blog\/category\/microsoft\/windows\/windows-10\/"},"img":{"alt_text":"UEFI-only vs Legacy BIOS boot option","src":"https:\/\/i0.wp.com\/www.winhelponline.com\/blog\/wp-content\/uploads\/2024\/05\/bios-uefi-legacy-boot-modes.jpg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.winhelponline.com\/blog\/wp-content\/uploads\/2024\/05\/bios-uefi-legacy-boot-modes.jpg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/www.winhelponline.com\/blog\/wp-content\/uploads\/2024\/05\/bios-uefi-legacy-boot-modes.jpg?resize=525%2C300&ssl=1 1.5x, https:\/\/i0.wp.com\/www.winhelponline.com\/blog\/wp-content\/uploads\/2024\/05\/bios-uefi-legacy-boot-modes.jpg?resize=700%2C400&ssl=1 2x"},"classes":[]},{"id":17918,"url":"https:\/\/www.winhelponline.com\/blog\/we-couldnt-update-system-reserved-partition-error-windows-10\/","url_meta":{"origin":75809,"position":4},"title":"[Fix] \u201cWe couldn\u2019t update system reserved partition\u201d Error updating Windows","author":"Ramesh","date":"August 16, 2020","format":false,"excerpt":"When upgrading to Windows 10 or 11 from Windows 7, 8, or 8.1, or updating Windows 10 or 11, you might encounter the error We couldn\u2019t update system reserved partition, or error 0xc1900104, or error code 0x800f0922. Update: If you're receiving the \"We couldn\u2019t update system reserved partition\u201d error or\u2026","rel":"","context":"In "Windows"","block_context":{"text":"Windows","link":"https:\/\/www.winhelponline.com\/blog\/category\/microsoft\/windows\/"},"img":{"alt_text":"We couldn\u2019t update system reserved partition","src":"https:\/\/i0.wp.com\/www.winhelponline.com\/blog\/wp-content\/uploads\/2020\/08\/system-reserved-partition-error-upgrade.png?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.winhelponline.com\/blog\/wp-content\/uploads\/2020\/08\/system-reserved-partition-error-upgrade.png?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/www.winhelponline.com\/blog\/wp-content\/uploads\/2020\/08\/system-reserved-partition-error-upgrade.png?resize=525%2C300&ssl=1 1.5x, https:\/\/i0.wp.com\/www.winhelponline.com\/blog\/wp-content\/uploads\/2020\/08\/system-reserved-partition-error-upgrade.png?resize=700%2C400&ssl=1 2x"},"classes":[]},{"id":74926,"url":"https:\/\/www.winhelponline.com\/blog\/reagentc-exe-operation-failed-2\/","url_meta":{"origin":75809,"position":5},"title":"REAGENTC.EXE: Operation failed: Error 2 or Error 3bc3","author":"Ramesh","date":"April 24, 2024","format":false,"excerpt":"When you attempt to enable Windows RE by running the reagentc \/enable command, the following error may be shown: REAGENTC.EXE: Operation failed: 2 REAGENTC.EXE: An error has occurred. (or) REAGENTC.EXE: Operation failed: 3bc3 or REAGENTC.EXE: Unable to update Boot Configuration Data. The ReAgent.log may record the following error: Info [ReAgentc.exe]\u2026","rel":"","context":"In "Windows 10"","block_context":{"text":"Windows 10","link":"https:\/\/www.winhelponline.com\/blog\/category\/microsoft\/windows\/windows-10\/"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]}],"_links":{"self":[{"href":"https:\/\/www.winhelponline.com\/blog\/wp-json\/wp\/v2\/posts\/75809","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.winhelponline.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.winhelponline.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.winhelponline.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.winhelponline.com\/blog\/wp-json\/wp\/v2\/comments?post=75809"}],"version-history":[{"count":0,"href":"https:\/\/www.winhelponline.com\/blog\/wp-json\/wp\/v2\/posts\/75809\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.winhelponline.com\/blog\/wp-json\/wp\/v2\/media?parent=75809"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.winhelponline.com\/blog\/wp-json\/wp\/v2\/categories?post=75809"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.winhelponline.com\/blog\/wp-json\/wp\/v2\/tags?post=75809"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}