Virus on my computer

So i have a virus on my computer, keeps popping up as some fake antivirus program. I tried scanning with malewarebytes and it doesnt let me, it changes the path of the program and i cant open it. What are my other options?

 

use system restore or reinstall windows

 

dont have a way to back up my computer, and dont want to lose all of my files :s

 

System restore will take your computer back to the last update. It won't erase any files that you have obtained since then, but will delete programs and anything else added to your hard drive.

 

unless you do a complete system restore; it gives you the option to choose.

 

What OS?

If it's Windows XP, there's a wonderful tool called SmitFraudFix designed specifically for these types of "viruses."

http://siri.geekstogo.com/SmitfraudFix.php

Don't use it if you're not running XP though.