I/O Intensive Crashes

I have been having some system instability lately-mostly in I/O intensive apps like ripping/composing DVD's and actually crashed during defrag last night. System starts to reboot and when it gets to OS load, I get NON-SYSTEM DISK error. If I shut down w/ power button, boots up fine, and runs decent afterward. I'm wondering if this might be a HDD wearing out, or CPU/PSU heat issue as the room with the comp. in it is much hotter in summer than in winter. I haven't tried reducing my OC yet, because I really want to keep the speed up if possible. What do you all think?

[Signature Sux now that all my stuff's old-Damn!] Athlon XP 1900 (11x200) 42C (Load w/AX-7 & 8cm Tornado) - MSI K7N2 Delta - Corsair Value PC3200 - Gainward GF3 @ 250/550 - 80Gb WD 8Mb Cache -

During CPU-intensive non-graphics apps, I've seen the CPU overheat, less frequently I've seen the RAM overheat, and once in a while I've seen a power supply overheat (but usually with a power off). Very rarely I've also seen the controller chips on hard drives overheat, stopping access.

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