Mysterious special effects lag while gaming

First off I'll apologize if this isn't the place to ***** about my hardware problems, but I didn't see a "help, my **** is broke" section to the forum and this issue only comes up when gaming.

The problem I'm getting is a complete mystery to me. I bought a pretty decent computer (not the type for building one) that should have been fine for most games.

Mainly, I play a lot of TF2 and Killing Floor on Steam. I'm not sure exactly when it all started happening, but I recently bought a D-Link wireless router so I could play Wii and Xbox wirelessly on the side.

I noticed some lag in Killing Floor at this point. It started negligable, but about ten-twenty minutes in it would get bad enough to start just skipping and totally unplayable. This happened with other games like Beat Hazard as well wherein it got so bad while I was trying to exit the game that it took me five minutes to do so.

So I unplugged the router. Killing Floor and Beat Hazard got a lot better, though by "better" I just mean it takes a lot longer for the problem to occur.

I went back to playing TF2. And I think I'm beginning to see where this is going. I can play lag free, until anything happens close up. If I play Pyro, or an explosion goes off next to me, it lags. If an enemy is right in my face? Lag. If they're across the room trading pistol fire with my engineer, nothing.

And the last example recently is that I've been playing through Half Life 2. Totally lag free, until the Headcrab bombs. When the bombs open, they billow a smoke effect. If the smoke is onscreen, ridiculous lag that was not there before.

I thought it might be a RAM issue, but I've got 4mhz. I've played TF2 absolutely flawlessly when I first downloaded it on this PC. My virus protection is up to date at the moment, so at this point I really have no idea what's wrong.
 
Back