I was almost pretty sure that I was going to change my OS from Microsoft windows XP to Ubuntu which suddenly all my works came to live again in windows and it came back to normal.
The problem began when I saw a process (which was a system process) began using of 99 percent of my cup usage, not allowing other processes to run, once I had the same problem which caused by a virus named blaster (I think, and the fix from symantec can be found here).
Although being confident of my updated anti viruses, again I decided to test all my hard drive for viruses and nothing was found while searching Internet for the "SVCHOST CPU USAGE" didn't help me a lot since I got redirected to blaster solutions, but finally I find a page that said it is a new issue with micorosft update which make svchost use that much of cpu, also it affects the update program of windows so whenever you are using windows update your system gonna hang.
So do you need any better idea for writing a virus than this ? you can not update your files since the update program is affected and you can not almost do anything since your cpu is totally dedicated to a special process, and those all from microsoft which you trusted it for the updates.
I was thinking the only part that can be revised and it could be the trust part, so I may hesitate to trust Microsoft totally but I can trust a lot of people developing an open source operating system, I don't need to pay money, I won't get any viruses, the problesm will solved quicker and ....
Why not switching to ubuntu ? I'm going to switch, may be it's a better idea for some time to have a dual boot on a PC and after a while if you see you can do all your stuff with Ubuntu why not just delete micorosft and get rid of that.