I Need Help

I am having a problem, i cant open most programs, when I try it goes into ms-dos or somthing, i cant really try all the things on that sticky, coz if i download anything i cant open it anyway, I know the name off the file that is doing it, it is called Slass.exe. no, not lsass.exe . its in system32, and if i try to delete or cut it, it says its in use. i really need help. feel free to ask any questions, or tell me what i can do.