[glc - nice price on that fan at Directron, hard to find those anywhere locally. Almost have to order online to get those fans]
Kristi - Glad that it "sounds" like it's not the hard drive
. . . My cousins had some BigFoots in their Aptivas that went south at about the same age as yours (they were running K6-2 500s) - that's why I suspected the drive most.
Because of the age of the system, and all the heat-related system errors, and just to cover all the bases, I'd still recommend downloading & running the disk diagnostics. Just to make sure. I'd also recommend (like others have) backing up as much of what you really want to keep while you have this chance. I don't think the Quantums have a history of long life - in general. Here's the link for the Powermax disk diagnostic program
http://www.maxtor.com/en/support/downloads/powermax.htm
It looks like this version works for all Maxtor as well a legacy Quantum drives (no more hunting around for the older drive test software). That download webpage has all the instructions - you'll want to read them carefully, to make sure you only test the drive [and not go wild with a low-level format = which completely erases all data - without full backups!]
It's too bad that the hard drive and the cpu fan are so noisy in that system, because the little old 70w power supply shouldn't make any noise at all. Sometimes an older power supply like that I replace the exhaust fan - just for the sake of peace and quiet.
When you're ready to put the new cpu fan on, see if you can blow out the dust from the heatsink before you attach the new fan. And a little dab of thermal compound on the cpu just under the heatsink, like glc recommended, should help lower the temperatures a little too. Those K6-2s were some of the first processors that we started to really have to pay attention to cooling with. (My kids and I are still running some K6-2s and K6-IIIs here at home)
Best of luck
. . . Gary