Whats wrong - power supply?

Some of you guys may know that I'm currently stuck in Germany on internship, with only my crappy old Cyrix system for company (computer-wise )

Well, it has a pretty big problem that's p!ssing me off. Here goes...

Firstly, spec:
Cyrix MII-333 processor
128Mb PC66 RAM
Unknown motherboard - MSI perhaps
32Mb Riva TNT2 mach 64 PCI graphics
Win XP Pro Corp (!)

Secondly, problem:
Basically, I've always had a problem where the computer decides to crash randomly, normally pretty nastily (had tha machine since '97). At first, I thought it was Win 98 1st Ed crashing it. It wasn't, as I had the same probs when I upgraded.
Next I thought it could be mobo, or more likely cpu (I'd heard these are ****). Or maybe RAM - anyway, I never found out, just put up with the crashing.

So, I cart it over to Germany and leave my good PC at home with the parentals. And it's **** - can't play games or anything. I used to have a Voodoo 2 in it, and it could just about manage UT and Delta Force. But stupid me gave the card to my (now ex) girlfriend's dad when I build my new one. So, it had crappy ATI Rage Pro 8Mb (more about this in a minute).

Big probs

So, I have it here, but want to play Starcraft and Red Alert on LAN with a couple of mates - the pc will handle these games.

I buy a network card and install it, and turn it on and... nothing. It turned out I'd blown the power supply (crappy old 150W one anyway). I think this was because in Germany there is no on/off switch at the mains and I just plugged it straight in with the power supply turned on at the back, and boom, or more precisely fizz, it went.

So I bought a new 250W power supply - nameless and probably crap as its a sh!tty old pc anyway. I put the power supply into my machine and hey presto it worked fine again. But performance was still crap.

Getting to the point

Remember I said it only had 8Mb ATI Rage Pro graphics? Well I got a PCI TNT 2 from ebay and installed it. This is when the big problems started.

Although it crashed randomly anyway, I now had/have a new problem - the damn thing takes about 10 attempts to turn on.

I turn on the PC and it becomes powered, but it won't post. the hdd spins up, as does the cdrom drive, but no post. There are 4 ways to make it boot up, way 2 if way 1 doesn't work, and likewise with 3 if 2 doesn't work, and 4 if 3 doesn't work:
1) Keep resetting it a few times. After the nth time of resetting it, it just decides to post and boot up as normal.
2) Turn the power supply off at the back and turn it back on. Try again. If not post on first attempt, try resetting a few times (this is normally the one that works)
3) Turn off the power supply at the back, remove the power cable completely, then turn on and if no post, rest a few times until it does post.
4) Repeat 3 until it does post.

Phew! What a bugger it is to get going! As the problem started since I put the graphics card in, I thought that maybe someone on ebay sold me a duff card. It just seems strange that if the pc boots up, the card works fine, I have never seen a situation where the graphics card stops bootup.

Or, it could be the power supply - taking out and reinserting the power cable normally allows it to boot up. But it was fine before I installed the graphics card.

I'm pretty sure that the system is not sucking too much power from the power supply - after all, I only have a crappy old chip, DVD Drive, HDD, LAN Card and my graphics card. And besides a 150W supply worked fin for years, with a Voodoo 2 in there.

So what could the problem be? Graphics card? Power supply? Something else?

Oh, and I don't want to throw the PC away, as it is my very first ever computer. Oh, and if you've read this far, thank you!!!