At the desktop, right click on My Computer.
Click on properties.
Choose or click 'Advanced System Settings'.
Select the 'Advanced' tab.
Under 'Start up and Recovery' select 'Settings'
Uncheck 'automatically restart'
Next time the OS shuts the system down with BSOD, write down the error codes and post the error codes here.
I am on VISTA 64 at the moment, but my instructions should work for Windows XP if that is the OS you are using.
While it is probably hardware I'd say don't forget to check system/application logs.
Likely some unknown driver/voltage etc issue but always worth a shot.
Check all cables.
Run a temp/voltage logger.
Yeah I know you've already done a ton but I tend to start with stupid easy things first.
Sounds like now you've replaced everything but your case cd-roms and HDD's.
You stated what you did in the past but since new install have you redone the prime95 etc?
I know there is one test for cpu one for ram.
Could be your cpu just remembered it was about the only thing you didn't change or maybe changing it's FSB/voltage around could make it more stable. Try to avoid spending more money =P Although it gives you a reason to upgrade, I use to only upgrade when I fried my systems.(I lost 3 systems due to power failures, melted surge strip,(2x lightning strikes) bad luck and cheap rent in poorly wired places is bad.
Which reminds me, check your input power/surge strip/monitor voltage. During the summer with AC's brownouts etc you could be dipping.
I've had my one monitor turn off along with my desk lamp 5 times this week while my 2nd monitor and pc managed to stay on(bigger capacitors I guess).
I've seen things like this in the past where the only thing we could come up with was the power source. Getting a UPS can help smooth out your supply, if it will run. If not, make the landlord fix the power.