If you disable then re-enable the usb hubs they aren't reinstalled. Unhook all your usb devices (use a PS/2 keyboard and mouse), right-click => uninstall (not just disable) all the usb root hubs and usb controllers in the device manager then restart the computer and see how it goes.
If you want you can analyze the kernel memory to try to find the specific driver that's using the cpu. Check these links :
http://support.microsoft.com/kb/q177415
Kernel memory is steadily increasing until system hangs
This is another useful tool :
http://technet.microsoft.com/en-us/s.../bb896653.aspx
If you go to view => show lower pane and click on system on the top left you'll see a list of the kernel dll's with their description. Google the names of the ones that are not registered by Microsoft to make sure there's nothing wrong there. You can add other columns to monitor the memory used by each process if you go to view => select columns.
If the svchost processes seem to use too much cpu use tasklist and the instructions herein to see what services are underneath each svchost process :
http://www.raymond.cc/blog/archives/...ows-task-list/
To reinstall from scratch :
You need to have a firewall (part of SP2) before you connect to the internet (turn the router off or unplug the ethernet cable in the mean time), so if SP2 is not integrated on the MCE CD you'll need to install SP2 and enable the firewall. If your MCE CD is already patched with SP1 (look on the CD or go to start => run and type winver once Windows has been installed) you can install SP3 right away, no need to install SP2.
So prepare the drivers and the needed service packs on a CD (or on an usb drive, the usb ports should work right away, but maybe at a limited speed if SP2 isn't installed yet). Then install Windows MCE, install the latest versions of the drivers, install SP3, enable the firewall, connect to windows update, install the latest critical updates and see how it goes