Problems when building a computer for my little brother

[Pyong Kawaguchi]

I have the computer built, all with fully compatible parts, but unfortunately, when I turn it on, it will boot normally, but with no video, the 8400gs doesn't show anything at all, but the computer gives no beeps to show errors. It also has onboard video though, now, just wondering, if I were to take out the internal bios battery, then put it back in a few seconds later, would it reset the bios and have it set so that it uses onboard video as default, rather than the PCI-E video card?
Also, the power supply and the ram are from another computer, which gave the exact same results when starting it.
What would it be, the ram, the power supply or the video card?
Thanks in advance. :)

[MetKiller Joe]

Are there PCI-E power sockets on the graphics card? Did you plug those in? Did you make sure there was a tight fight with the motherboard?

[TheGhost]

You don't have to take out the battery. You should just be able to pop the card out and see if it boots. Most computers will run without a dedicated video card to varying degrees of graphical capabilities. Try that out and see if it works. If it does, then it's something with your video card - it may not be getting powered or it may not be seated correctly, or it may just be DoA.

[Abdurahman]

The 8400gs is a low end card, it does not have a power connector. Either you did not set the option for using the card instead of onboard in the bios, or the card is DoA

[Pyong Kawaguchi]

I reset the bios/cmos and when I start it, no beeps and no video.
And, my main pc died too D:
I started it up, and poof, smoke everywhere :(

[Cojafoji]

I reset the bios/cmos and when I start it, no beeps and no video.
And, my main pc died too D:
I started it up, and poof, smoke everywhere :(
Damn dude, you are having SHIT luck with the computer gods...

Also, that card sounds DoA son, RMA that shit!

[Pyong Kawaguchi]

Oh, btw, I got new parts :D
Quad Core 3.20ghz ^.^