did much of everything that was said on the thread on steam website. I ran my memtest, and i think i have a bad slot. I tested varius RAM sticks, (2x512) ina ll 3 slots, and the only time i had an error was when a single stick was in my first slot. So i removed both sticks from the 1st slot and have them sitting in 2 and 3. Ran HL-2 fine for 30minutes or so with no errors. Clean as a whistle. hope my new PSU will solve the random comp. restarts when it arrives, although none have happend in a little while.
Thanks for the help and ill keep up with replies.