Scan Prompts For Disk - Correct CD

Intel Dual Core 2.4Ghz / XP MCE SP2.Running sfc /scannow I get the following message that is well documented on this forum and elsewhere: "Files that are required for Windows to run properly must be copied to the DLL Cache. Insert your Windows XP Professional SP2 CD-ROM now."My problem is that I know I am using the correct CD, and I can't see why Slipstreaming should be necessary, but I still get the error.Some history:01 New PC supplied from manufacturer with XP MCE SP2 backup disk02 Reformatted the HDDs and rebuilt the PC how I wanted it to be using this backup disk to load the o/s03 After installing a particular application I startedto get odd behaviour so ran sfc /scannow04 The error reported above occurred so I checked that the CD has a full i386 directory (it does, of course given I used it to build the PC)