svchost.exe is a generic host process name for services that are run from dynamic link libraries (dll files).
any number of things could cause this (including a couple of semi-nasty viruses)
check the event viewer to see if there is more info there
Are you running Win2k, XP...?
try scanning for viruses after checking the event log
if that doesn't help, try stripping the system down to bare essential hardware and reinstalling the hardware one piece at a time with non-beta drivers (driver corruption sometimes causes this error)