I have one of the above running at 100% which slows the computer right down. If I right click and end process the computer runs normally till the next boot. I have run my own AV and have also done a couple of online scans with no virus detected. also use adaware, S&D anda few other antispyware again nothing unuual noted, appreciate sugestions XPPRo plenty of RAM nothing unusual done, other than removing Yahoo messenger which gave a few probs but has gone
Have you tried reinstalling Yahoo and see if this cures the problem,i know you do not want this on your system...but this may be a pointer if it is causing the 100%.Or even System restore may be worth a shot.
Reason I ask is that a friend of mine had a similar issue a while ago. After a bit of fiddling around we found another instance of svchost.exe in another folder. Turned out this was some monitoring software which was recording all keystokes and running applications and firing information of to a website. We deleted off the system and solved the problem.
You need to identify which service(s) is/are associated with the instance of svchost that's using your CPU. Download Process Explorer from click here This program runs from it's own folder, no need to install it. When you open the program, hover your mouse over the instance of svchost using your CPU and a small window will appear giving you the information. It could be Automatic Updates, for example, downloading updates to your computer.