Extremely Low Framerates / Frequent game slowdowns
With the kind of processing/rending going on in game engines, games these days are usually system resource hogs. If you’ve got a pretty aged system, or even a mid-leveled one, you’ve probably faced a lot of slowdown in games which have at times rendered them unplayable. If your framerate slows down like a slideshow, you’re facing what a million other gamers like you are, the solution to which isn’t really that specific (unfortunately).
Solution:
When your game engine gets too much to render or process, it will slow down like hell. To ensure that it never gets more work than it can handle, you can start by bumping down a few of your in game settings. One of the main setting that screws up frame rates is your Draw Distance. Try and reduce it to as low as you can bear to live with. If you wish to optimize your game further, try bumping each setting down one at a time, and see which has the maximum effect on your game.
There are a lot of games out there that aren’t too well optimized. Such games have crappy frame rates and stutter like hell on even the best rigs out there. If you’re up against such a game, your best bet would be to get it patched or update your graphic card drivers. If that doesn’t work either, try looking for background processes that might be hampering your game’s performance by hogging up too many system resources. Such processes could include spyware or other malicious software; if you suspect that your PC’s infected, check out Jayesh’s article for a few programs that can help you out.
This is one of the most interesting articles I've come across in a long time. Very cool stuff! 
