The Disk Defragmenter in Windows 7 and Windows Vista is scheduled to run every Wednesday at 1:00 AM. This article tells you how to disable the defragmenter schedule in case you’ve installed a third-party defragmenter, or modify the schedule accordingly.
Disk Defragmenter Scheduled Task
Click Start, type dfrgui.exe and press {ENTER}. When you are prompted for an administrator password or confirmation, type the password or provide confirmation. To disable defragmenter schedule, uncheck the following option:
If you’re using Windows Vista, enable the Run on a schedule (recommended) checkbox, and click OK
In case you want to modify the defragmenter schedule, click the Modify schedule… button, and select the frequency, time in the resulting dialog.
If you’re using Windows 7, the user interface varies a bit, and appears as below:
Schedule is enabled by default. In case its disabled in your system, click the Turn on schedule… button.
Click the Run on a schedule (recommended) checkbox, and there you can modify the day and time accordingly.
I’ve used the "Browse" button to locate the Windows Command Processor, but I have to select it from the list of "Program." The "Always use the selected program to open this kind of file" check box is grayed out. I don’t even know why Windows has decided cmd is a file to be opened by an external application. This problem happens if there is a file named CMD in your profile folder, and Windows tries to execute it when you type CMD (without the .exe suffix, the file extension) in Start, Run dialog. 