OK, I will help as best I can with the question you asked. SFC will require the same version of the files as is installed in order to complete the repair. If there is no local/cached copy it will require media, and you must ensure that this media is the same as the version of XP (ie, SP3/etc).
Have a read of
http://support.microsoft.com/kb/900910 and
http://support.microsoft.com/kb/885522 for some information regarding modifying registry keys to point to a local media location. The fact that SP2 is referenced on the 2nd link may indicate that this workaround is not required for SP3 and so if you are using SP3 then you can perhaps store the media centrally and configure registry to connect to a share for these files.
Hope this helps.