Since my AVG was useless, I uninstalled it and went for Avast free version. I scanned my pc and the cause was win32 sality.
I then deleted all the viruses.
Now, all my games (before this problem occured) was running smoothly.
If I install a game and run it, my cpu becomes too slow.I will double click a game and nothing happens.I will check task manager and my process is there.
I just installed oblivion and Strongholds 2.
And I checked task manager.
I saw rundll32.exe taking 100% CPU usage together with oblivion.exe.