Says DLL not a valid windows image,

Hello,
When I boot up my XP laptop (Dell), this appears: ISASS.exe bad image The application or DLL C:\Program 1\
Google\GOOGLE~1\ GOEC62~1.DLL is not a valid windows image. Please check against your installation diskette.

Then every file I have on desk top or that I try to pull up gives a beep, and says Bad Image. Everything is a bad image. I do not know what to call the virus. I was told it is a virus that renames your exe files, and is hard to get rid of. My AVG does not detect it. Please advise....