Please Help: Nothing will run

Hello,
I recently obtained a virus and ran some antivirus software and was able to get rid of it. After getting rid of it my Itunes will not open. When I try to open it I get an error message stating C:\Program Files (x86)\itunes\itunes.exe Application not found. Another problem i'm running into is that Firefox won't open. Whenever I try to open it it ask me what program do I wnat to open it with. I choose internet explorer and nothing happens. If you guys can help me out with some suggestions to this problem it would be greatly appreciated. I also wasn't sure where to post this.