Yes - I'm going to use the Mac word...
I did a little reading and there seems to be consensus in the aluminum chassis Mac world that Vista runs hotter by several degrees than OS X in the same box.
Some Windows (and Mac) users users seem to like SpeedFan to monitor and adjust CPU fan speeds. Increase fan speed for Vista or just let SpeedFan adjust itself to keep the CPU temps about the same.
For XP vs. Vista, some folks notice that the temp on their CPU may go up slightly (3-5 c) with Vista, but the video card temps always
seem to go up (2-4 c) with Vista. The theory is the more advanced 3D Vista graphics or some such...
Can Vista be made to run in a less graphically intense mode? Are you sure the reading is from the CPU and not graphics?
Some Windows users say after a while of idle, the Vista CPU cools down a couple degrees and levels off.
Some but not all of these people are overclockers.
It is most curious but I can't test anytime soon. If you can confirm think heat shuts it down and you have checked all the obvious, maybe SpeedFan will help you. Better fan, maybe some Prestone.http://www.almico.com/speedfan.php
I realize now that I have no idea what my CPU temp or fan speed is