I'm using a 5 years old ASUS K53SV with Win 7 using a Nvidia GT540M GPU.
Recently, especially when playing games, everything runs smoothly, but after a while, usually a few minutes, there's a half second freeze, and then the performances get terrible, usually less than 20 FPS on medium settings. And everytime I launch a game after, the performances will be outright awful.
Lowering the graphical settings doesn't change anything, the only solution is to restart the computer every time.
My drivers are up to date, I selected the Nvidia card as the default GPU and not the integrated Intel chip, temperatures are OK.