diagnose my hardware problem

I just installed a new 200 gb hard drive, and everything was going fine for a few days. Then I tried to do a file system benchmark with Sisoft Sandra and the computer shut down. When I turned it on again, it never got to the POST or BIOS. The monitor stayed blank the whole time and acted as though it wasnt connected to anything. All the various fans were on, and the CD drive could open and close by pressing the button. I could only shut it off by holding the power button for like 10 seconds, or hitting the switch on the power supply. It was like this all night last night, as I was trying various things, and then this morning I tried it and it started up normally. I don't think it's a power supply thing because I only swapped in the new 200 GB for my old 60 GB, so it's not like I added a whole new component. And my PSU is an Enermax 350W that hasn't given me any problems.My info:
ASUS A7V 333
Athlon 2000+
80 GB Maxtor HD
200 GB Maxtor HD
GeForce3 Ti200
CD read/write and DVD read drive

if ur turning on ur PC and not getting to the POST

i would say its a board problem

ive even seen it where its the IDE controller but i doubt it

can u get power at all in ur machine, try unplugging a couple devices to see if it really is a wattage problem

Well, as I said, it's working now just fine, started normally, with everything plugged in. I suspect if I started doing something intense again like the hard drive benchmark test it might crash and be unresponsive again. I didn't mention it before, but right after I installed the new hard drive, I transferred everything from the old hard drive over to it, and in the middle of it the computer crashed, but that time it rebooted normally right away.

what size power supply do u have and what size case, ya heat is a bitch when it comes to PC's

i love my ThermalTake case with 152 fans lol

Bah, it just happened again. Though this time it came back on after about 10 minutes. This time I wasn't doing anything particularly strenuous, so it's weird. I did watch my temperatures via Asus Probe, and they did seem a little high, normally CPU temp is around 50C, now averages around 55, and sometimes goes up to 65. However, I don't overclock, CPU or GPU, and all the fans are working. I have a cheap case, the only fans are on the CPU, GPU, and power supply. The power supply is a 350W ATX Enermax. The voltages are as follows:

+12V = 12.8
+5V = 4.919
+3.3V = 3.28
Vcore = 1.792

Is it possible a faulty hard drive could cause a temperature increase? Because I bought this new hard drive from one of those "repackaged" places.

Too quick to call hardware problem. When you get in the PC you bump things around, first thing you should do is Reset everything. memory and all the PCI cards. Not getting to post is usually only a hardware problem if it NEVER gets to post. But in this case it sounds like it sneaks through to post every once in a while. Like I said though, first reseat everything.

Also, when it is in this state, try to make it think. What I mean is, make it beep. There are lots of ways to do this but I usually just yank the video card and turn it on. If I still don't get a beep code I yank the memory too. Anything to get it to communicate. Then put it all back in and try again. If it still has this problem I would check into a BIOS update.

Like I said. Don't be too quick to call hardware bad. I have seen WAY too many good pieces of hardware coming back as warranty repairs. Last count we had 50% of hardware that came back was actually bad.