Gateway fx510x desktop issues

hi, i have a gateway fx510x that I've had for about 5 months. i use it for a backup PC, so it doesn't get a lot of use.

when i have used it, it's been a great machine.......until now.

now when i press the start button, i immediately get three beeps, and no display on the monitor. the monitors sleep light stays on. it never turns green to show that the PC is sending information to it.

i had a friend look at it, and was told that the power supply had failed. so i just put a new power supply in it, and i get the same three beeps on start up.

I've not been able to find out what the three beeps are telling me. i can't get any information on the beep codes doing a google search.

the motherboard is a OEMD975XWT2G1

does anyone have any suggestions on what i need to do / check to troubleshoot this PC ??

thanks,
ron