Big problems with my K7N420 Pro

Question

I've been having what is apparantly a hardware problem with my computer. Randomly the thing just resets. About once a day. Sometimes more, sometimes it goes for several days without resetting. I check the temperature in BIOS setup whenever I catch it resetting, and the CPU temp (CPU is 1700+ XP) is always between 140 and 150, not an unusual temperature (is it?)
I got to thinking that maybe the temperature does have something to do with it, so I set to blowing out the dust, thinking that should help. So I blow all around with some canned air, I close it back up, and turn it on - but something else happens. During POST the computer freezes, right at the line where it tells you how much memory you have. I reboot. It works. I run the system restore from the XP installation CD from boot, thinking "just in case it was Windows crashing all along". It freezes in mid-operation. I also start to smell something burning, you know that horrible smell of plastic burning, I'm sure. Now I panic and shut it down. I crack it open trying to determine where the smell is coming from, but can't figure out where. I boot again, with the case open, hoping to catch a stronger smell (suspecting the PSU.) Instead of booting it beeps in my ear, several very long beeps. I can't tell if they are supposed to be one continuous beep, so I can't tell what they are supposed to mean. The manual doesn't have an entry for that code. The lights in back showed one green light in the upper left, all others red. The manual says that means "Early Chipset Initialization". What the hell does that mean?
Can anyone here put these symptoms together for me and tell me what is wrong with my computer? Did I just cause another problem when I used the canned air, or was this likely a new symptom of whatever problem was causing the random reboots? Is the problem likely the PSU? Thanks.

Answer 1

Okay so I think I jumped to conclusions with my last message. I was tired, it was a long day, I wanted to make some quick progress in little time before I crashed (no pun intended.)
Since the configuration Slot 1: Crucial stick, Slot 2: Kingston stick, Slot 3: empty caused big problems, and Slot 1: Crucial stick, Slots 2 and 3: empty, did not, I started to wonder if I could be jumping to another conclusion, and if the problem could be on the motherboard somehow. So I tried the configuration Slot 1: Kingston stick, Slots 2 and 3: empty, and it POSTS fine! And just to confirm, I stick the Crucial stick into Slot 2, and the thing won't POST properly. First three attempts, the computer won't even activate the monitor, the fourth and fifth, it does activate the monitor, but the initial BIOS screen (the one where the memory is checked in the POST when you disable quick boot) looks all corrupted-like, with strange characters littered across the screen. I stuck the Crucial in Slot 3 to see what that would do, and the first time it freezes around 88MB during the RAM check (I left quick boot disabled), the second time it POSTS successfully.
So maybe something on the motherboard went bad such that using Slots 2 and 3 causes these problems. This model is pretty old, so does this problem sound familiar? Is it possible? I don't know the hardware architecture well enough to guess whether it's likely.
(I have BIOS revision 2.7)
EDIT: And after trying all those configurations, going back to the original configuration, (Slot 1: Crucial, Slot 2: Kingston), it STILL beeps at me like before.
EDIT EDIT: *sigh* and now, trying the second configuration again (Slot 1: Crucial, Slots 2 and 3 empty) just so I can use the computer again, I get errors when I try to boot. Booting to the OS I already had installed, I get the Windows screen with the moving blue boxes, and then after that nothing, and whenever I try to install a new copy of the OS from disc or repair I get a BSOD. It says IRQL_NOT_LESS_OR_EQUAL. I've no idea what that means.