If you need to execute repair O.S. command:
sfc /scannow
you need to copy cdrom binaries to different path (with XP/2003 you need to copy i386 folder to c:)
To give the ability that sfc command will search for local binaries on different path you need to change register settings:
HKEY_LOCAL_MACHINE \ SOFTWARE \ Microsoft \ Windows \ CurrentVersion \ Setup \ SourcePath.
