A very generic canned speech, and you answered some things already..
List all components.
List the cooling setup and heatsink.
When did the problem start?
How many running proccesses?
what anti virus and anti spyware programs are you running?
Update Windows, all Drivers and all Scan definitions for protection programs.
Use MSconfig and google to uncheck all unneeded start up entries.
Go through this guide, complete all steps.
Its spyware guide, not video card thing..
Download and run speedfan list tempartures it gives.
Download and run regseeker. Then Disk Clean up, then Disk Defrag. (Or whatever program you use, Diskkeeper or O&O)