This is an older Dell Optiplex 330 Running win 7 to run some older programs. Recently, it's been shutting down and upon reboot stating Shut down due to thermal event. This ONLY happens when booting into windows. When I booted from a diagnostic USB stick it stayed on all weekend without shutting down. When I ran Dell Diagnositc (f12) it went through the whole hour long process, did not shut down and did not come up with any issues. I opened it up, cleaned it out, replaced with new thermal paste, the heatsink doesn't get overly hot to the touch upon start up, and the thermal event ONLY happens when booting into Windows, either full boot or safe mode. The machine also ran from a Live USB Ubuntu without issue. Could it just be a driver issue? Im usually very good at figuring this stuff out but this one has me stumped. Thanks in advance.