Sinister crashing

[Salvatorian]

I finished stalker with a bad ending and felt like playing it again in puruit of a more satisfying ending but now Im experiencing these bad ass crashes especialy in the dark valley. The first time I played the game, it used to crash once every 2 hours or so but now its under a few minutes.

Heres my rig (yea its old, but gives me a stable smooth frame rate)

AMD 1.8 gigz
1GB DDR
128 MB nVIDIA 6200TC

Any help would be much appreciated