low fps. don't know why.

So, I've had this computer for at least a year now, and I don't understand why my frames are dropping below 20. I used to get 40-80 and now it's awful for TF2 (I've dropped my gfx settings as low as I can, except the resolution, in an attempt to compensate, but it hasn't helped) and in L4D I not only have low fps, but my game will randomly freeze for a period of 5-10 seconds. I don't know why it's doing this all of a sudden.

I can't think of any recent changes that would have this effect, and I don't know how I should try to fix it?

Help?

defrag the game to start.
How old in the windows install?

I defragged the game and even did a full reinstall about a week ago. no help.

windows install is probably a couple years old.

and I thought I had this part of it resolved, but it came back again tonight... it's taking an inordinately long period of time to load the game, and joining a server also takes quite a while.

It probably has something to do with your RAM...

Try using registry cleaner, clear out your cache and look for things that make be taking up CPU usage in the background. Do a virus scan.

If all else fails, format.

I am having a similar problem. Very low fps when I first join games and it locks up a lot - more than it should be, and more than it did before I formatted my computer.