For the love of God, change your RAM! Its one of the cheapest fixes you can do! Honestly, this has sounded like RAM all along (crashing during games at the same spot, etc.) Wouldn't hurt to expand your RAM size too.
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Intel P4 3.4GHz
2GB RAM (533MHz)
RAID performance Hard Drive (320 GB)
ATI x800 XT (overclocked)
SB Audigy
Sony 19" LCD (X-Brite)