Windows 7: Every installed program no longer starting

I have a very strange problem just occurred on one Windows 7 desktop. I was using a software VOIP phone on it, when the PC put itself to sleep after 10 minutes, presumably according to my power saving plan.



When I tried to wake the computer with a keypress, I got the message the computer was not shutdown normally. I chose to start normally. Then I got the message Windows 7 could not start normally, but there was an option to repair start up files, which I chose. A window came up suggesting it might take an hour to fix, so I went away to use another phone.

When I came back Windows had booted to the desktop, but whenever I try to start a program I get the message:

"The application has failed to start because its side-by-side configuration is incorrect. Please see the application event log or use the command line sxtrace tool for more detail."

This error occurs now with everything : games, Firefox, IE, MS Office, email client. The only thing still working is Notepad and the 2D Windows games.

I had a look to see if there was a recent restore point I could go back to and I was given this message:
"No restore points have been created on your computer's system drive."

I had a default home premium install so I think there should have been restore points..

Anyway this is an internet surfing and gaming computer. My documents are on my own partitions. Any help would be appreciated, but if I can't get it going by Christmas I shall probably format the partition and reinstall Windows.

Welcome
Start with a clean boot, maybe that will help solve the mystery.
http://support.microsoft.com/kb/929135
If that has no affect, try in safe mode as a test. Lets see what the problem is

Run your antivirus updated and full scan
Download and run malwarebytes, full scan and updated.

Thanks for your answer richc46.

I went through the clean boot procedure, which made no difference. I always keep a close eye on msconfig and the only startup items were ATI drivers anyway. Safe mode : yes. Started..

I began a full scan with MS Security Essentials but after 45 minutes it seems a full scan might take 6-8 hours. Malwarebytes will not install. I get the same message:
"The application has failed to start because its side-by-side configuration is incorrect. Please see the application event log or use the command line sxtrace tool for more detail."

TBH I think a virus is a very low possibility. I keep MSSE up to date and had Malwarebytes installed until recently. I indulge in very low risk behaviour. Even my web browsing is with Firefox with adblock plus, no-script etc

UPDATE : I am commencing to format the Windows partition and reinstall 7. It should only take six hours or so to reinstalll everything.