I'm an A+ certified PC Technician and have run into this problem countless times and seem to have started since the release of Microsoft Update. Microsoft Update combines both Windows and Office Updates together. The result is 100% CPU utilization for prolonged periods. If you're not doing anything and the CPU is 100% or you hear your CPU fan kick in like an airplane taxing down the runway at takeoff, chances are good that Automatic Update is checking for Windows/Office Updates. Microsoft has a "hotfix" that claims to fix this but it's not publicly available for download and prompts you to call Microsoft to get it. Well, I did call Microsoft and it was like pulling teeth to get it. The 3 different technicians I spoke to cite other local factors, like malware (virus, trojan horse, adware, spyware, etc) or other CPU intensive programs running at startup. With a little more force and less patience, I asked to skip the troubleshooting and go right to the hotfix. Surprisingly, none of the Microsoft technicians were able to get to it and kept transferring me to someone else in India (OK, OK, maybe it was Bangladesh) who gave me the same answer. After a lot of head scratching, I was finally E-mailed the "hotfix" but it was password protected, and only good for two weeks. So, basically useless for helping others out over a long period of time. To my surprise, the fix was actually a patch for the hotfix, so it did absolutely no good without having the original fix. I gave up trying to make Microsoft Update work. Here's the manual fix:
The first step may not apply if you don't have Microsoft Update installed:
Go to Windows Update.
On the left side, click the link "Change settings".
Check the box "Disable Microsoft Update software and let me use Windows Update only".
Click "Apply changes now".
Now, onto the slightly technical part:
Right click My Computer and click Manage.
Click the + next to Services and Applications.
Click Services.
Right click Automatic Update and choose Stop. Keep this window open, as you'll need to come back for the last step.
Open up Windows Explorer and browse to %WinDir%\SoftwareDistribution\DataStore. Note: %WinDir% is usually C:\Windows or C:\WinNT
Delete the contents of DataStore.
Lastly, go back to the Computer management window and right click Automatic Update and choose Start.
No reboots are necessary and I'd be very surprised if this doesn't fix the issue with SVCHost.exe running 100% CPU time.
Theory:
Using Process XP (a souped up Task Manager browsing Processes) shows that when CPU utilization is 100% that SVCHost.exe is married to @ 2 DOZEN different services. I can't think of any reason why one single process should have that much association with other services. Most processes link to at most 1/2 dozen services. It's no doubt that CPU's are busy with that much linked association. I truly hope Microsoft identifies and repairs the code to their Microsoft Update. I now have to remember to manually run Office Updates separately. Good luck to you all.
For more information:
http://support.microsoft.com/kb/916089 
Unsolved 
