Help with overheating? (If that's actually the problem...)Follow

My computer (Dell Inspiron 1720 (laptop), just over 3 years old) didn't use to have an overheating problem, but now I'm pretty sure it does. I first noticed it when playing LOTRO. It used to be that the game would momentarily freeze and my Wi-fi connection would die. That didn't sound like overheating to me... until I also got that thing where objects would swap textures, you'd be looking at a guy who looks like he's wearing wallpaper wrapped over his whole body while giant faces appear in the walls. That, I've heard, is a sure sign of overheating.

Buying a GearHead fan to put under the laptop made it happen slightly less often. I also have problems with Battlefield: Bad Company 2. After about 15 minutes playing, my framerate would drop, my ping would skyrocket, objects would change colors (green rocks, white guns), trees would float (or the ground would disappear), triangular chunks of a light teal color appear on screen, converging at the center. Oddly enough, while my ping does shoot way up, I never disconnect like I did when playing LOTRO. I've even disconnected while playing a game that doesn't use the Internet, though I was also downloading something at the time.

The problem is unpredictable. Sometimes the fan does nothing. Sometimes I deliberately try to make it overheat by moving my computer outside during the summer on a particularly hot day, with very little wind, and it runs fine. I only discovered RIFT today, and I really want to try it out someday, but I've stopped playing games on my PC because of this problem. I can't find any place in my laptop to open and clean dust out that doesn't scream "warranty-voiding" and worry me a lot about damaging something. I have actually removed the keyboard to upgrade the RAM in this thing (the problem seemed to start right around the time I replaced the RAM, but I put the old chips back in and the problem persisted), but that didn't give me access to any fans or anything.

Does anyone have any ideas, or think they know what else this might be? I apologize if there's some simple thing I've missed.

I don't know if there's any data Speed Fan collects other than what's on the front tab, but here it is. Readings while surfing the web:
http://img571.imageshack.us/img571/2198/speedfan1.png
Readings while playing Bad Company 2 on low graphics:
http://img202.imageshack.us/img202/8438/speedfan2.png

Yeah, definitely overheating. Have you tried blowing out the vents with compressed air (with the computer off)? If you don't have the expertise to take it apart and clean it out, that's basically all you can do other than taking it to a shop to open up.