Inspiron 8600 Heat Issue?

I have 4 year old 8600 with 2 512mb SIMMs installed. If both slots have a SIMM, after about a half hour, the computer crashes and I face a blue screen. If I take either SIMM out, the computer runs fine indefinitely. It doesn't matter which SIMM slot I pull the memory from. With one removed, I can run all the pre-boot diagnostics with no faults. With both installed, I get memory related faults, if not immediately, after the crash. Am I correct in thinking this is heat related and probably a motherboard issue? The way I figure it, I have the following choices?
1. Run with 512mb? Slow.
2. Replace the mother board? Probably ~$150?
3. Replace the single SIMM with a 1024mb SIMM but wonder if that will result in the same fault?
4. Replace the computer? Don't really want that hastle yet.
Any thoughts would be really appreciated. The bottom line, fill both mem slots and it eventually faults. Remove either SIMM from any slot and it runs fine, albeit slow. I apologize for repeating myself but so does the problem and since my hair is thinning, I'm starting to draw blood from the scratching. Thanks.

 

Have you run any memory diagnostics? http://www.memtest86.com/
Also, when is the last time you have cleaned out your fan/vents? You should probably blast it with some canned air to clear them out, they tend to clog quickly.

 

I had a 600m and I inserted a second DIMM (2x512mb), and then many times I would get these graphical glitches on the screen, like parts of the screen would disappaer, and sometimes I would have to reboot to get it working again. And the area right under the DIMMs was pretty hot, so I have always tilted the laptop by propping something in the back...

 

Your suggestion is a good one. I keep the 8600 on a slanted stand that leaves the underside elevated a little less than an inch. This is all start happening when I installed a webcam. I just wonder if the thing was stressing the computer? What are your thoughts of going to a single 1gig module?

 

I've not run memtest but I did give the interior a good blown air cleaning, which I was surprised to see it relatively clean. Few small dust balls here and there. What are your thoughts of a singe 1gig mem module?

 

Is the stand covering the entire bottom surface of the laptop? I prop it up so the underside is free, and if you want you can put a small fan to blow air underneath. Going with one SODIMM, I am not sure if that is better. But it makes sense since one SODIMM *should* not generate as much heat as two of them. Are both of them at the same speed? Try the memtest first. Have you also tried running with the other 512mb only (take out the current one, run just the other one)?

 

Mine is propped up also. Yes, both are the same speed. One is Dell, the other Kingston. I've tried all combinations of one or two SODIMMs in the slots. I'll try the memtest. thx, TL