There isn't a syst.host process as a part of Windows, could you mean svchost.exe? That's a generic wrapper for services, some of which love to run heavy on occasion.
In task manager, right click the offending process and select "go to services" and list them here.
On the other hand, if it really is syst.host, you can ask task manager to open the file location and see what it's associated with, but it could also be a virus.
Eating more cheese on Thursdays.