Computer works fine, til I put in Geforce 8500gt

I recentally fixed a computer that took a huge dive on me. Tested every piece, piece by piece making sure everything worked. Recentally put it all back together and resolved one of the major issues I was having.

CPU was overheating and making the fan on it run at 4500 rpm. Opened that all out, realized it was a ceramic thermal compound, so I cleaned it off, put in silver, whamo, down 20 degrees Celcius.

I'm thinking the CPU running that hot for a long time did a number on the power supply. But I'll get to that.

My problem is, the Graphics Card I had in this machine a Nvidia Geforce 8500gt 256 mb worked great for this machine before the computer all took a dive. Now the second I plug this into a full set up I know works, the computer shuts down if its on, and just will not reboot.

I'm thinking its a power supply issue, but I wanted to bounce this off some of you guys. The power supply is a 400w power supply, the standard one that Comes in the HP m7100y that I own.

So what I did is I ordered a 500w power supply, more than enough to power my system.

I'm currently running 1 Dvd/CD RW drive, one basic cd drive, a 160g sata harddrive, a soundblaster audio card, and the Pentium 4 3.00ghz/mobo that came with this system.

Am I right to assume that the Geforce 8500 is eating up too much of my power? Or do I have a different problem on my hands?

Thanks for your time in advance.

And the power supply hookups on the MOBO are only a 24 pin, and the 4 pin for the CPU. There is not spot to plug in the 6 pin I know a lot of video cards need, and there isn't a hook up on the card for more power either.

http://www.newegg.com/Product/Prod [...] 6817148027

This is what I ordered.

Found out some great information lately through trial and error.

This computer came with a ATI graphics card, that continued to "work" even when it didn't, meaning the computer still did its thing when the card was shot.

I put an Nvidia in, thinking hot damn, better. For the most part it was, but Nvidias have something built into the chip set, that when the card fries, the computer doesn't turn on, to protect any damage from the motherboard.

The graphics card was shot. (Tested the card on four different pci-e slots on dif PCs, same result everytime, no boot.)

Ordered a brand new one for around 40 bucks that does the same job that I wanted it too.

Problem solved.

Thanks for help, and the PSU I had before had a blown cap in it.