I have a Sony Vaio laptop (VPC - F22L1E, sometimes listed as F22L1E/B), with a 1 GB GeForce GT 540M graphics card.
The GPU heats from room temp. to about 55°C with just booting and surfing on the web. I was playing a game that I played lots of times before, without problems. After a minute or so, there are sudden decreases in the fps, lasting for only a second or two, which I think is throttling. GPU-z logs revealed that this causes the temperature to drop to ~70°C from 89°C. And the GPU core clock goes from 670.8 MHz to 202.5 MHz.
I can't remember the exact timeline, but I made a few changes to my computer: added an extra 4 GB RAM, upgraded to Windows 8 (from 7), then recently made a clean install of Windows 8 due to problems caused by upgrade, and made sequential updates to the nVidia driver. I remember to be able to play the game smoothly after the Windows 8 upgrade. And the RAM upgrade was even before that.
I could not open up the laptop to see whether the fan is clogged with dust, but when I opened up the RAM module compartment, I saw no dust on that part of the main board. (I know that dust is more likely to accumulate around the fan, though.)
A friend thinks that it is because of the summer weather (around 25°C now), but what am I supposed to do, only use my computer in winter, in which case the temperature would be 17-20°C indoors.)
What could be the problem, and what can I do?
Edit: I should add that after the clean Windows 8 install, some features, such as fn hotkeys, did not work even when I installed all drivers available on Sony's site. It seemed as though all of drivers available for Windows 7 were not available for Windows 8. I contacted Sony support, and they told me that the device did not support Windows 8. (Why they have most of the drivers for Windows 8 is a mystery to me.) This had not been an issue for the Windows 8 upgrade, though. Maybe some of the Windows 7 drivers were retained and kept working.