XP startup problem

I have XP Pro installed on a Dell laptop. It had been working fine for a long time. Suddenly it stops at startup with error message " Windows could not start because the following file is missing or corrupt: System32\Drivers\PCI.sys". When I try to perform a repair by booting from CD I get another error message saying "File Setupdd.sys could nor be loaded. The error code is 4."
Any suggestion would be appreciated.