As a hardcore gamer I've been looking forward to a new rig. Guided by a positive review of an ABS system I got one myself. Nice specs, 640 MB or video, excellent processor...
The surprise came when the system came out of the box. The system is constantly crashing with an unreproducable frequency. It has been doing so through: a hard drive replacement, re-install of OS, without any non-MSFT software, after re-seating memory, running memory and board diagnostics, all the latest drivers on all devices. Yes, one would say it's your fault for putting Vista on - fool! True, but the DELL computer I got for my wife, with nearly the same specs, has yet to crash - with the same OS. Here, clearly, hardware is at fault and ABS.com (ABS Systems) would not take the system back. I've wasted over 80 man hours trying to work out the kinks. Many hours with support, many hours on my own. In real life I live and breathe software as a software engineer and I've built a number of rigs in the past.
My biggest regret is going with with ABS Systems. Let this serve you as a warning.
I'm using my work laptop to type this message, because using the system built by ABS.com may result in a crash before I can send this.
A few things I can think of. First, as Avevm suggested, try a different psu. If the psu is bad, nothing else can work properly. Next thing I would look at is the motherboard.
Of course, the whole name of this thread is strange. "Why you should build your own rig", and then you go on to tell how a Dell works properly? I mean, if the Dell works properly, then that is a reason to buy a ready built computer instead of build one. Maybe it would have been better to complain about ABS.