My computer hates me

My computer is starting to overheat and automatically shut down--again. >_< I had this problem last year, and thought it was gone.

Recently I installed a temperature monitor as part of an attempt at undervolting my laptop. Unfortunately, due to the fact that the Intel Celeron is a gutted piece of hardware junk, that's not possible. So my battery life remains short (which is fine, I can live with that), and my CPU continues to run hot. Apparently I can't live with that.

The temperature monitor occasionally gets up to 42°C (it starts off around 30°C, and typically hovers around 35° to 40°). But for some strange reason, it will spontaneously shut down on me even though it is below 42°! (This is the part that bugs me--sometimes it won't shutdown, but at other times it has apparently decided it has overheated and does. If a computer fails, it should at least fail consistently! <_< ). I'm not doing all that much when it overheats either--nothing at all resource-intensive. It's annoying.

Alas, I don't know what I'm going to do. I cannot afford a better computer. I could take it in, but I've done that before and I foresee the unfortunate and harrying situation in which they send it in for "repairs". This leaves me without a computer for two to three weeks, during which time they don't find anything wrong with it and I have to pay (or worse, they do find something wrong with it, "fix" it under warranty, and then when I get it back it isn't actually fixed). I've complained to CompuSmart about this before, and I feel bad complaining so much, even though I am the customer.

If the problem doesn't go away after school is over, though, I think I might have no other recourse but to send it in. Right now I've got a fan running beside me to cool off the computer (did I mention that I have a cooling mat beneath it, but it still overheats?!), however, I consider this situation untenable (not to mention noisy).