Inactive windows explorer crashes, vista theme changes to basic, s

[Inactive] windows explorer crashes, vista theme changes to basic, s

about 2 days ago i left my pc alone and someone used it, now it has a virus ( believe) i have macafee and have done 5 fukk scans untilnnothing popped up. internet explorer crashes on start up, windows explorer crashes, the windows start bar and theme changes to basic (i have cista) by itslef like 1 hour after turning on my pc. internet explorer doesnt respond to the "back" or "home" buton" it just doesnt work properly, it's not update issues. everything was perfect until 2 days ago. please help i only have this laptop and i need it for school (im in college) i dont know much. when i type something in "RUN" it say that it failed to start up. i tried to go to the event viewer and even that fails to start up. regedit smc dont work