Since I put my latest system together, I've had random lockups, making it difficult to work or play games. I've finally gotten the solution, it seems....
Asus P4C800E-Dlx M/B
2x512MB (1GB) PC3200 DDR RAM
160GB SATA HD
Pioneer 104 DVD-R drive
Radeon 9800 Pro (Has external power connector)
Audigy Sound Card
The case had a 400W PS, with good ratings for the amps on the +12V and +5V rails (this is important, btw).
I figured I was pretty well set, but every once and a while, the system wuld not boot the first time or two, requiring a reset. There was also the issue with the lockups, which happened seemingly at random. I did attempt to replace the power supply with a 550W PS bought at a computer show, but it didn't last long, and the seller didn't have a replacement (cash back, instead)
Recently, the startups got worse.... graphical corruption, as well as freezes during startup. I felt it was related to the video card, in some manner, but as I said, the PS had good amperage ratings on the important rails. Still, I suspected that the PS, supplied with the case, might not be as good as the ratings on the label, so I went in search of a better power supply.
In my research, StarTech makes a nice 500W power supply, with good amperage for the "important" rails - ATI recommends 24+amps on the +12V rail, and I think you really want over 30A on the +5V rail. My backup plan would be the more expensive Antec. Unfortunately, the only way to get the StarTech was through postal, and I didn't want to wait, so I travelled to my local CompUSA...
Of course, the don't stock anything "good" but Antec at CompUSA, but I spotted two other candidates: CompUSA "House brand" 500W PS and a ThermalTake 560W PS. After looking at the CUSA 500W, I quickly ruled it out (18A +12V rail, ugh), but the ThermalTake didn't have the ratings on the box, which was shrinkwrapped. After arguing with the girl working there ("Only wattage matters, look, sir, I've been building computers for 10 years" - me:"Well, I've been building PCs for almost 20 years, and ATI says the rail amps are important!" and so on...) - whatever happened to "The Customer Is Always Right!"???
Anyway, the ThermalTake barely eked out 22A on the +12V rail, a big disappointment for a 560W power supply, once I convinced her to look it up on the net.
Grabbing a 430W Antec "TruePower" (Same price, basically, as the ThermalTake - ~$100) I saw what I wanted... 26A on the +12V rail, 36A on the +5V rail, SATA power connectors, dual fans with temperature sensing technology to keep them quiet.
After getting home with it last night, I installed it, also being pleasantly surprised with the special power connectors included for extra fans (I have two in the chassis) and even an EXTERNAL power connector! Solidly built, this bad boy was heavier than most power supplies I've handled.
Since firing it up last night, not a single lockup and it started up without a single glitch. It might be too early to tell, but I think this did the trick. My PC would not normally stay up the entire night without freezing up.
In short: Get a QUALITY power supply, if you have a power-hungry system (with a P4 MB and/or a powerful video card). Research it! Amps on the rails are important!!! Watt ratings really are not a good indicator of how adequate a power supply may be in a given system.