Just noticed this thread, sorry for the delay Monty but since you're still around I guess I can still answer it.
This link may help :
http://wiki.djlizard.net/Product_IDs
To do a repair installation (or run the system file checker) you'll need the exact same version of Windows as what the user has installed : if he has Home SP2 you'll need an XP Home SP2 CD. In case of retail installations, any retail CD that's the right version will work. But in case of an OEM installation you'll need an OEM CD from the same manufacturer and preferably for the same computer model since those CD's usually include specific softwares and drivers. For instance the sata controller driver will be included on an OEM CD while a retail CD may fail to detect the hard drive. If you can't get the OEM CD,
here's a work-around to load the sata drivers on laptops that don't have a floppy drive.
If there's a recovery partition on the drive you can still create the recovery CD's (you'll need them if you want to run the system file checker) or see if there's a non-destructive recovery option.
Both sfc and a repair install replace some files and leave other files untouched. If you use a CD that's the wrong version you may run into compatibility issues between the restored files and the files that weren't modified. You can 't do much about the installed updates that are not part of a service pack yet (though there are ways to
create a CD with all the latest critical security updates), which is why the first thing to do after a repair install is to connect to Windows update.
If the user has updated XP with SP2 (or soon SP3) but only has an SP1 or prior CD then you can slipstream the latest service pack into the CD using one of these method :
http://www.winsupersite.com/showcase/windowsxp_sp2_slipstream.asp
http://www.helpwithwindows.com/WindowsXP/winxp-sp2-bootcd.html
http://www.geekgirls.com/windowsxp_slipstream.htm
For the system file checker to run properly there has to be some folder called i386 in the root of the XP CD. With most OEM or recovery CD's there's no such folder. The i386 folder can then usually be found somewhere else on the CD or on the computer's hard drive (often in C:\i386\ or C:\Windows\i386\). You have to modify a setting in the registry to tell sfc to look in that location. Run the registry editor and navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Setup. Double-click the "SourcePath" entry and change its value to the folder holding the i386 folder : if it's C:\Windows\i386 then sourcepath has to be C:\Windows\. Reboot the computer and run sfc /scannow.
