help just built a computer and there is no display

i just built a computer and there is no display. i noticed that when i boot the computer the hard drive powers on as well as the fans and the dvd drive. the status light flickers as if the processor is doing something. But the mouse, keyboard does not function and the motherboard does not have a on board video card so i used one from my old computer and there is no display the monitor stays in stanby mode after i boot the computer, please help and tell me what could be the problem.

first i will tell you what all is in this computer

Asus M2N-SLI Motherboard - NVIDIA nForce 560 SLI, Socket AM2/AM2+, ATX, motherboard = Audio, PCI Express, Gigabit LAN, S/PDIF, USB 2.0, Firewire, Serial ATA, RAID
MPN: M2N-SLI

processor = CP1-AM2-6400A AMD Athlon 64 X2 6400+ Processor ADX6400CZBOX - 3.20GHz, 2 x 1MB Cache, 1000MHz (2000 MT/s) FSB, Windsor, Dual-Core, Retail, Socket AM2, Processor
MPN: ADX6400CZBOX

hard disk drive = Seagate Barracuda 7200.10 250GB Hard Drive - 7200, 16MB, Serial ATA-300, OEM

ram = OCZ SLI-Ready Edition Dual Channel 2048MB PC6400 DDR2 800MHz Memory (2 x 1024MB)

dvd rom drive = Lite-On LH-20A1S SuperAllwrite SATA DVD Burner - 20x DVD±R Burn, 16x DVD±R Read, 8x DVD+RW, 6x DVD-RW, 8x DVD±R DL, 12x DVD-RAM, 48x32x CD-R/RW

and a 380 watt powersupply that i bought from the local computer repair shop

 

Did you remember to attach the 4-pin power connctor to your CPU?

 

yes everything is connected properly i was thinking that the motherboard is bad

 

you should change the power supply before doing any of that because it doesn't sond like you have a very good one. Getting a decent power supply is far more important than a good processor memory etc..