i'm having some problems with my computer, it wont turn on, and i was wondering if overheating can cause a computer to block itself to turn on?

Not likely, unless it shuts down on its own and immediately you try to power it back on.

What type of hardware are we dealing with here? What are the temps like?

Absolutely!

With some motherboards, if it decides a CPU is clocked "too high", it will refuse to boot up... even beep. The only way to get it back in this case is to clear the CMOS and reset your processor speed in the BIOS. The "Auto" setting should always work because it will "downshift" until it finds a setting that boots.

I have a Soyo MB with the fastest processor that it supports installed... an AMD XP 3200+. You can't "overclock" when the fastest settings already match your CPU. If I "manually" enter the maximum settings, I get the same refusal to boot. But if I use "Auto", it boots just fine at max speed (don't ask me why).

I got a feeling we're talking about some cheap motherboards :P

I can get my comp to boot up at whatever speeds on my 2.4Ghz (yes, I've tried the max). It gets incredibly hot tho, and I'll never run it at those temps, I think the fastest I'll dare run my comp (which runs 24/7) is at 3.2Ghz. Which is a massive overclock. Of course, I'm not running the standard HSF.....