MiniMatt

From recollection SVCHOST.EXE is used to allow certain DLL files to run as executable services. That is, a perfectly clean computer can end up running SVCHOST multiple times, so it's not necessarily a bad sign, though that's not to say it can't get abused by a virus. Laptops running Win XP seem particularly keen on running multiple copies of SVCHOST, mainly through all the extra system tray power management applications and the like they run.

So, scan for viruses with up to date AV software (crucial), all of them catch viruses about as well as the next although Norton, and lately Mcafee, seem intent on installing a ton of extra gunk as well which does nothing for system performance. Certainly don't go deleting SVCHOST.EXE as, whilst it can be infected by a virus like any other, under normal conditions it will still show in task manager multiple times and it is a crucial Windows system file.