I've been having troubles for the past 6+ months. exactly 8months ago I installed an Nvidia 9500GT video card and would be able to run games on max settings like AC:2,LFD:2,League of Legends,Counter Strike:Source/etc until one random day I started to get random fps drops that lasted 1-3mins sometimes 5. I'm not sure what could have caused it since I've never installed anything else besides the video card so I'm wondering what can I do to fix this problem?
it might be wore and tear on your video card but it might also be that some other part is not performing as well as it use to. with that it could also be a software related issue. did you install anything and/or change any setting on the OS before this happened?