If u have complete backup of setup CD of WinXP in ur system,WHICH IS OF SAME VERSION AS THAT OF XP INSTALLED IN UR SYSTEM,then see this page to run sfc without using CD at all.This requires a small Reg tweak.
http://www.updatexp.com/scannow-sfc.html
It's better u backup the Registry before applying above tweak, do this:-
Go toStart>Run, type Regedit and press Enter.
There in Registry Menu, Select "Export Registry file" option and export the Registry as a File.
Or, while making changes (as mentioned in the above link) to the registry, u simply copy the Default Keys present there and do the changes.
After Registry tweak, u can get the reqiured files from the backup in the system itself.
If u have problems/doubts with Registry editing,then go for the CD from which u installed the Windows previously, to perform sfc.