Your airflow sounds like it should be just fine.
Aren't 120mm fans great? I can't wait for my second 120mm to be delivered.
But yeah, temperature <i>is</i> important, though mostly just because in the past AMD's CPUs <i>really</i> didn't take to overheating very well. At least now there's shut-off protection and on-die thermal diodes to monitor the temps, which helps a lot. (Though still not as elegant as Intel's P4 solution.)
But I've personally found that instaiblity itself is quite often just an insufficient power supply and/or a funky stick of RAM. It's rarely heat and if it is heat even then it's most often overheating of the video card or the RAM, not the CPU. Good airflow through the case does wonders for correcting any of these kinds of problems.
So as long as your processor isn't frying, your case has good airflow, and your power supply meets the demands of your hardware, then you're rocking.
Of course nothing will save you from bad drivers though.
If you buy hardware from a company that hires monkeys to write their firmware then you're pretty screwed no matter what you do. Luckily those kinds of issues only come out whenever significant OS changes occur. (Such as when Microsoft introduced Windows 2000 and the hardware vendors were all going nuts trying to write drivers for it because the old Win9x ones weren't usable for Win2K.) Since WinXP is based on the same technology as Win2K, we've seen a pretty nice stretch of time now where only really bad companies have bad drivers for their hardware.
But anywho it sounds to me like you've found the line between stability and BSODs for your system and you're good to go. You could try to lower your temps, but it probably won't do much for you.
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