explorer.exe and netshell.dll

Good day.

I have computers issues... At first this may sound like some hardware issues, but it will eventually turn into software issues as well, which are more immediate, I guess.

A friend of mine and I built my computer back in May. It's using the following components:

AMD Sempron-64 3100+ Processor
MSI RS482M-IL S.754 Motherboard
Mushkin 1GB PC3200 DDR RAM
Antec Sonata II w/ 450W Power Supply (with a fan that doesn't want to start...)

After installing Windows XP SP2 on it, I kept getting blue screens with all different types of messages; for example,
TARGET_MDL_TOO_SMALL
and complaining about win32k.sys and a listing a bunch of hex numbers,
PAGE_FAULT_IN_NONPAGED_AREA, etc.
Sometimes it wouldn't give me an error name, just a hex address for something that was apparently wrong.

I did a memtest check, and found that my RAM was bad, had it replaced, still got the blue screens though less frequently, but the memtest was saying my new RAM was good. Maybe I have to slow my RAM down or something? If I do, I don't know how.

So, I've suffered with these periodic blue screens of almost-death probably once every one or two weeks. I should probably have had it fixed by now, but I'm stupid like that, kind of like how I never go to the doctor... After the last such episode (last night), I'm getting the following errors:

"Windows Explorer has encountered a problem and needs to close, blah blah."

Error signature:
AppName: explorer.exe AppVer: 6.0.2900.2649 ModName: netshell.dll
ModVer: 5.1.2600.2767 Offset: 000052a0

Also getting a "Generic Host Service" type thing erroring and closing down. That will happen just once, but explorer.exe will repeatedly close and reopen. If I don't click "ok" on any of the error messages, things will work for a bit, but then my sound drivers will stop working, etc., after a while.

Technical info for the Explorer error and a HijackThis log are attached.

Any assistance would be great; specifically for the explorer problem, but if anyone has any ideas for the hardware problem, I'm all ears. Thanks for your time.