Originally posted by: werk
This is getting ridiculous.  2 days now and I cannot play this game.  I get pretty much every error discussed on the 
halflife2.net, 
hl fallout, and 
steam forums.  Memory errors, crashing to desktop, restarts, hanging to black screen, artifacting, stuttering, etc.
System:
Ideq 200v sff
Athlon XP 1600+ (soon to be replaced with a 3000+, not that I think it'll help)
ATI Radeon 9800 Pro
768 MB PC 2700 (name brand crucial and kingston)
80 GB Seagate 7200 rpm ATA drive
Dell 1900FP LCD
I have all the latest drivers 
Latest via 4in1s (also tried older versions)
Latest Catalyst (still need to try Omega drivers)
DirectX 9.0c
SP2/all latest updates (also tried no sp's/updates)
So far I've tried:
Every console tweak listed, in different combinations
Defragging HD
Deleted all game content and registry entries, uninstalled steam, redownloaded HL2
Windows reinstall (currently, there is nothing on this system but XP, all updates, drivers and 3DMark2003)
Only running 512MB stick, either slot
Running system with huge desk fan blowing into it (although temps were reported as OK previously)
Underclocking 9800/processor
Every resolution/quality combo I can (most times it crashes when trying to change resolution though)
Probably some other stuff I've forgotten by now
It's not heat or PSU issues as I ran it through 3DMark several times last night.  
This is driving me insane, I get memory errors if I try to change resolution, crashes at random times, memory errors at random times, stuttering at random times.
So far, the farthest I've gotten is seeing the strider walk by right after you get out of the train station.
:| 
Next step is to switch everything around with my MCE machine (SN41G2) and see if an NVidia chipset fares better...oh boy, I'm really looking forward to reinstalling windows 2 more times.