Well, not a waste of time exactly, but it will not straighten out any files you think are missing or corrupt from your Windows system folders (except dllcache). It f-e-e-e-e-ls good! I will never even suggest running it for any problem (I used to before I knew better).
I have not slipstreamed in a while but one of these other Bleepers can point to the most current instructions, which if you carefully follow, will work the first time.
What I did was take my Windows SP2 installation CD, downloaded SP3, then (following the good directions I found here) made a new folder on my system and merged the two pieces into one, then from that, made a new Windows XP installation CD with SP3 already on it. Keep that new CD handy for future problems or use it for your sfc /scannow runs. Save your old Windows XP SP2 CD for some rainy day.
Then I copied my entire SP3 CD out to an external drive and told sfc /scannow to look for files there when doing it's comparison check. In all my experimentings, it is easier for me to just have the Windows XP SP3 installation on an external drive so I never have to pull out CDs.
I think I used the following article to modify my system to tell sfc /scannow to look on my external drive. Some of the discussion leads you to think that sfc /scannow will replace missing or corrupt "system" files, but it does not. If your system came with SP3 installed, there may also be an up to date i386 folder on another partition and you can tell sfc /scannow to look there.
If you think you are having some system problem - if you are seeing some weirdness and feel that running sfc /scannow is the first thing to do, it will not help you unless you are missing files from your dllcache folder and you would probably not know that. You can empty your dllcache folder of the protected 3498 files and your system will still work just fine. If you run sfc /scannow successfully, it will repopulate the emptied dllcache folder - that is what it does. sfc /scannow only cares about keeping the dllcache folder up to date.
Files that come "into play" for running XP are mostly (not all of course) going to be in the %Systemroot%\system or %Systemroot%\system32 folder and sfc /scannow is only concerned about missing or corrupt files in this folder:
There was a time when I used to suggest running sfc /scannow but I never saw it actually fix anything. Mostly it just complained like yours did. Then when I learned how it really works and proved it to myself, I will never suggest running it for anything - it is a waste of time for troubleshooting (but feels good). If it ever does find anything to do, you have some other problem to fix.
I attached the list of the 3498 files that Windows File Protection monitors on your running system and it is the same list that sfc /scannow uses when asked to check the dllcache folder (it IS the XP Protected File list). Rename or delete any one of those files on your healthy system and Windows File Protection will replace it. You will never get a chance to run sfc /scannow since Windows File Protection will replace the missing file in about 1 second.
Edited by joseibarra, 22 December 2010 - 07:08 AM.