Guys, I need your help. Basicly, now I have 2 computers. The one I am writing from now - Pentium III at 500 Mhz, matrox g200 8mb, 160 mb ram (dont laugh at the config, i use it for learning only ). and everything is working perfectly well. Recently, i bought the following hardware all seperately from ebay. first i got a geforce fx 5500, then i bought ASROCK P4S55FX+ Intel Celeron 2,4GHz + 512MB DDR , and then a new atx tower wit more supply. Now when i connect it all in the new pc, it doesnt work. I have never connected a whole pc from scartch, so i might be doing something wrong. i think the motherboard is working, since the fan of the cpu and the one from the video card seem to be working normally. Its not from the video card, cause i replaced it wit the matrox, the one i am using now, and still didnt work. i think i've got all the cables right, the big supply cable for the motherboard, the 20pin one, and i connected one of those small cables for the power sw. how can i know what is causing this? is it a problem wit the connections, or the compatibility? when i got the motherboard and the cpu, they were separated. i removed the old warming paste, and got a new one, and put it there too, so i guess thats not the problem. the cpu seemed to be in place.
 
 
P.S. I just noticed that the board says that it uses 2.5 V ddr ram, but the one i have is 2.6 V. do u think that could be the reason? if i remove all the ram, would the bios still start?
P.P.S also, the manual of the motherboard says not to use 3.3 V video cards cause it may permanently damage the board. i have no idea how much V the geforce is using

As well as the main 24 pin mobo connector, did you connect the 4 pin (2x2) one as well. The CPU has to have its own power supply to work.

i didnt connect it before 8O , but now when i do and when i start the computer, it gives a short bzzz sound and it nothing seems to be working. when i plug out the small connector again, and leave only the main one, it again starts without any bios, but wit working fans. so what do u think is the problem? cpu? ram? or motherboard?

I think you are on the right track. Put in the 2x2 power connector first.
Then leave only mobo, CPU and fan, and PSU and see if you get any beeps. If so, put the memory stick in, and reboot, and so on.
 
You are listening for 1 short beep on startup

by 'Put in the 2x2 power connector first.' u mean i only connect the 4-pin connector, without the main power supply?or, it matters in what order i connect it?

Sorry, I meant to say ensure the 24 pin and 4 pin ATX connectors are in