ok, i have a custom built computer with a AMD phenom 9950 quad-core, 4 gigs of dual channel RAM, cross fired 2 ATI 4870's, and for the mobo its a Gigabyte MA790X-DS4. i am running win7 also. i have this problem with one my CPU cores running about 80 to 90% just idling? i have a g15 keyboard also and i found out if i unplug it and plug it back in it stops so i uninstalled my keyboard and its drivers and restarted and it still was idling high. what gives?
Find out what process is eating up your CPU cycles. ctrl+shift+esc to task manager, go to processes, sort by CPU. Google the process that seems to be the culprit, act accordingly. (Malware -> kill it, system process -> find out what it does, if it's not needed kill it, some sort of program -> kill it if not necessary, else try to find an update)
FireScale rig: 955 BE @ 3.6GHz, NB @ 2.4GHz, HT @ 2.4GHz (need a new CPU cooler) Asus M4A88TD-V EVO/USB3 8GB DDR3-1333 @ 7-7-7-24 Asus HD5850 @ 800MHz core, 1050MHz RAM