XP Pro SP3 File Checker Broke

I updated my XP Pro SP2 with SP3 on a CD.Since then when I run sfc
/scannow,sfc freezes about 30 percent through.Am I missing something?How
does one update sfc to run on SP3?

When I re-boot, chkdsk finds many files in trouble but fixes.Not sure where
the log is so that I can review which files.I suspect the DLL cache is
messed up.

Didn't find anything on a Google search that helped.

I read that SP3 update would make arrangements in the DLL cache for sfc to
work.

The system runs OK afterward but sfc will not run.

Any help is certainly appreciated.