If you have a non-Microsoft (e.g., Dell) CD, and you attempt to run
sfc /scannow, sfc may report the CD is not the right one, even if you're sure. The reason is that Microsoft's own CD labels read "Windows XP Professional Service Pack 3 CD". If your CD is labelled something else,
sfc will fail to accept it. Here's how to change it.
Delete %windir%\inf\fp40ext.pnf
Open %windir%\inf\fp40ext.inf, and scroll down to the last ten lines in the file where you'll find these three lines:
WKS_CD_NAME = "Windows XP Professional CD-ROM"
SRV_CD_NAME = "Windows XP Server CD-ROM"
SP_CD_NAME = "Windows XP Professional Service Pack 3 CD"
Insert your WinXP (with SP3) CD in the drive; in Explorer's left pane, scroll down to the CD drive letter and write down the CD Title (mine reads "WIN_PRO_XP3").
Pick the one of the three text lines in step 2 that is related to the service pack you're trying to use.
Type a semicolon (";") in front of the line that you need to change. That makes it a comment, so it is no longer read by
sfc.
Duplicate the same value name, but type in the actual title from your CD. Here's what I did:
;SP_CD_NAME = "Windows XP Professional Service Pack 3 CD"
SP_CD_NAME = "XP_PRO_SP3"
Save the edited fp40ext.inf file, and retry sfc /scannow. It works!
