Pci.sys missing or corrupt...(I've tried everything)

I get the System32\drivers\pci.sys missing or corrupt message when trying to boot Windows XP. Now, I have tried going to my recovery console and tried "expand drive:\i386\pci.sy_ C:\winnt\system32\drivers /y" all I get is access denied. So, then I restart from XP disk and pressed enter to install Windows XP. Now I should get a repair "R" option, but I dont get that. It tells me that I have to format to install. There are some important data on C drive and hence I dont want to format the drive. Does anyone have other solutions? Thanks.

When you are trying for the new installation in order to reach the repair option, then does it show the fact that you have XP installed? Which version of XP are you using, is it OEM or Retail or upgrade or full?

You can also try other things, while in the recovery console before you expand type set AllowAllPaths=true and it will alow you to overwrite files in the directory C:\winnt, If that is the directory that XP is installed into.

You can restore the File by Using the Windows Recovery Console. Use the Windows 2000 Recovery Console to expand Pci.sy_ from the I386 folder on the Windows 2000 CD-ROM to the \%SystemRoot%\System32\Drivers folder on the hard disk. To do this, follow these steps given on the below page: http://support.microsoft.com/kb/319136