Watty

I am having a problem with my userinit.exe file. I recently recieved a virus that infected some of my exe and scr files. When I try to log into my computer the background will come up but I get an error message that says something about "userinit,exe error click ok to terminate the program." I have tried to run repair from my XP Pro disk but it tells me to plug in or cut the power on to my hard drive. When I go into CMOS it finds my hard drive. Does anybody have any suggestions.