Steam games lag


EGO Is My Life!
I am getting REALLY annoying lag spikes whenever I play any Steam game. even games like dod 1.6 and Cs 1.6 get lag spikes. I changed nothing on my computer and didnt install or delete anything. This just started randomly happening and all my other games work fine, like Guild Wars and CnC3 Tiberium Wars with settings maxed out. It also is not my internet ping. Any help?
If you have your netgraph up are you slowing down on FPS, choke, or loss? It sounds like connectivity problems.

Go ahead and try a Steam game on single player and see if you are having the same problems.
yes, sorry for not mentioning it before. I average around 90 most of the time with maxed settings. Every like 10 seconds, it drops to around 2-5 fps.
Do me a favor and get a graph running of your CPU usage. There might be a program eating up all your CPU cycles every once and a while.