Well, in your computer's registry, are several settings that are checked when you run scannow sfc.
As mentioned earlier in this article, the Windows File Protection service constantly monitors for any changes to the main system files. Well Windows XP keeps a cache (copy) of these essential files at the following location:
C:WINDOWS\System32\Dllcache (assuming C: is your system root which it probably is.)
NB - The dllcache folder is extremely important so Windows XP hides it from you! To view it go to: My Computer > Tools > Folder Options > View > "uncheck" Hide protected operating system files.
If that's the case on your computer then there is normally no need for the original XP CD to be inserted as your computer has a "copy" it can get hold of in this cache...
But, if the Dllcache folcer,or part of it, has become corrupted for some reason then you will be prompted for the XP CD - so your computer can get a clean copy!
Having said that not ALL installations of Windows XP have ALL the system files cached into this folder! You may only have around 50MB of files in this folder under Windows XP depending on the quota settings in the registry. (Under Windows 2003 Server the default is 300MB of system files!)
Annoying, YES!
Is there a workaround YES!
As well as having a cache of all the system files on your PC, I like to have the I386 folder from the XP CD installed on the computer as well. After doing this I then modify the registry to tell it the source path for these files... Why? Well not only does this prevent 99% of request for the the XP CD with Windows File Protection. But the I386 folder also contains many other files that are sometimes needed by the operating system and this stops those requests for the XP CD too!
NB - With today's large hard drives you are not going to notice this 475 MB folder on your computer, but older systems may not have the space for this...
Step 1
You will need to get your XP CD and locate the folder called:
I386
This is a major folder and should be one of the first you see, now copy this onto your hard drive into the system root. For most of you that is going to be C:\ so you should end up with a folder that looks like: C:\I386