After Windows XP SP1 was released, there are a large number of hotfixes released by Microsoft. Performing a repair or clean installation of XP erases all the hotfixes and Service Packs you've installed and you're forced to download them again. This is a frustrating task for dial-up users, who don't prefer downloading large quantity of data again. Here are two methods you can follow to download the updates locally (using a high-speed connection, preferably) and transfer them to a stand-alone system or a system using dial-up connection.
Windows XP SP2, a cumulative update containing all the updates is now released. See bottom of this page for the SP2 ordering link.
You can download all the updates that are
available from Automatic Updates by using the Windows Update Catalog. For
additional information about how to download updates from the Windows Update
Catalog, click the following article number to view the article in the
Microsoft Knowledge Base:
Source: MS-KB 283147 - Automatic Updates Downloads Cannot Be Installed on Other Computers
After downloading the updates, save them to a CD if you're planning to apply across multiple systems or a stand-alone system without internet connection. Before applying the downloaded updates, you can run through Windows Updates scan (don't download yet) to know the list of Critical Updates (Q######) pertaining to that particular computer. Note all of them to a piece of paper and install them one by one from the CD.
How to Install Multiple Windows Updates or Hotfixes with Only One Reboot
You can order the Windows XP Service Pack 2 in a CD from Microsoft.