I am installing the following computer:
L4VXA2 Rev 1.0 Motherboard
P4 2.4 GHZ Chip
3 Fans
1 512MB Ram DDR 333
1 Western Digital 20 GB HD
1 Benq DVD Rom
1 GForce 4 AGP Card 64MB

I know it's a low end Graphics PC but great to just do normal work on(MS Suite, Data Entry, etc) after I initially installed everything and booted up for the first time it went past post automatically. And started installing Windows XP in the middle of installing Windows XP SP2 the computer turned itself off. I said ok... and just pressed the power button again, it turned on and the lights flash for a sec on my keyboard and mouse and then go off, the light on my DVD read on blinks on and off, the HDD you can hear it spin, no beeps, no video. I tried changing the video card, and nothing, I tried removing the Ram to see if the beeping works and it does beep to let me know the ram isn't installed so I put it back, tried clearing the Bios/CMOS and nothing... I can't figure it out, I tried looking online and couldn't find any solution so now posting this in hopes to find someone that can help me. I even tried taking out the motherboard and putting it on a piece of cardboard and starting it just in case it was shorting on the case and nothing. Any ideas?

Before I forget my power supply is:

MODEL: ATX-450
450W
It came with the case.
I also tried switching that with one I have from IBest 400W with no luck

Check Video card or RAM

If you get no beep with the RAM installed and you get an error beep with the RAM removed, I would suggest trying another RAM stick.

When you get beeps, that is much better than not getting any beeps. The beeps indicate that the CPU is working.

this worked for me ; remove the battery too

problem