Hi.
This happens to me too, on my new Fujitsu Amilo - Win 7 - 32 bit (made in Germany please..lol).
It happens when I scroll down an Internet page, or have several internet pages open. I found on the net that it would happen less, if your Temporary Internet Files is empty (i.e. not cookies etc.)
I tried it and it does not happen when it's empty.
But reading all the issues here since 2009, I do think that Windows is the culprit.
Try the old good defragmenting, cleanup or even restore. And use a software to check your registry.
As I said, I don't get this problem so often (thank God), but performing the classic system maintenance can help.
So to resume... empty the Tempory Internet Files, fix Registry errors, perform cleanup and defragment, or try a System Restore (it's always my last weapon).
This problem has got nothing to do with heat.
If someone has other easy solutions, please let me know.