Windows 7: Programs not working correctly

Woke up yesterday morning to find I could not sign on to the internet.
Went to check email on MSN and it keeps telling me msn has stopped working.
I also had to re check the box in connection settings for LAN and DSL or it would go to dial up. Went to Firefox and it said Firefox is already running, but is not responding. To open a new window, you must first close the existing Firefox process, or restart your system.
So I restarted my computer. First thing that comes up is: Catalyst Control Center: Host application has stopped working. Msn and Firefox still were doing the same as above. Also quicken and quick books won't open. I downloaded and reinstalled Catatlyst, It opened after I did that but after I restarted my computer it stopped working again. I can get on the internet by using explorer but when I open it. It says A program on your computer has corrupted your default search provider settings for Internet Explorer. Also my weather channel app won't but displays a temp that is not even close to my area.

I ran a full virus scan and nothing.

I did set up another user account on my computer and everything works on it.

Thanks for any help. Kevin

Try doing a System Restore to a date before you had the problem. This will show you how to do it if you are not familiar. System Restore

Sorry I forgot to say I did do a system restore. Nothing changed.

Have you ran a sfc/scannow file check?

SFC /SCANNOW Command - System File Checker