gateway perf 1300 wont boot up

[kema00032]

I bought a second hand gateway performence 1300 computer ATXSTF manufactured in 2001. It only had 2 memory chips and a floppy drive. I added a hard drive and a cd-rom drive and a ethernet card. I doesnt have a place to plug in a monitor so i put a pci stealth 3d 2000 video card in it.
It looks like its in good condition but when i turn it on it beeps three times and then nothing. the cd-rom drive lights up and so does a light on the motherboard and i can hear the hard drive working. any ideas on what might be wrong?

[patio]

Bad or the wrong type of RAM.

[Aegis]

Did you change the RAM at all?  You don't mention it in the earlier description of what you did. 

You might remove the RAM, start the computer, and see if you get the beeps -- you should -- it's the computer's way of screaming, "I have no RAM!"

You might reseat the RAM chips -- sometimes that makes a difference.  You might put in one at a time, just to see if the system boots to one and not the other or both.