id like to start by saying thanks to anyone who helps me with this problem

ok, i just recently purchased parts for a new computer. im pretty good with putting them together from scratch, but this one has given me some trouble. i bought a Asus a8n-e motherboard with a stock 450-watt PSU, a Evga nVidia 7800Gt GRAPHICS card, 1 gig of RAM(2 sticks of 512), and a AMD 64-bit 3800+ 939 socket cpu. now i thought that the 450-watt was going to be enought, but i had heard rumors that the 7800Gt takes a sufficient amount to run. So on my fist set up i connected everything only to power up, and not get any reponse. so i sent it to a family friend technican to look at. he sent it back, saying it needed a bigger power supply, and that it would be easier to get one with a PCI-e connector already on it. So i went ahead and ordered a 580-watt PSU with 20+4 pin connector and a PCI-e connector. Now, when i go to power up the fans turn on and the light on the motherboard comes on, but there is no signal sent to the monitor keyboard or mouse. i tried to swap out different HDD's but to no AVAIL. There also in no beeping signal, like in terms of a beep code when i power up everything.Did the motherboard come with a manual? Does it say how large a PSU to use? Just covering the obvious here. ya, the motherboard does come with a manul, but i have yet to find a sepecification on the PSU requirement, but im assuming that 580 is more than neccessary. i mean, there is deffenently some power going to the mother board, because the light is lighting up. Everything else is lighting up as well, like the fans, they have LED's and those work. its just the video, the keyboard, and the mouse that refuse to power up, and i have tried different combinations of keyboards and different mouse's that i know work on other comupters.Strip it down to the basic - one RAM, plainest video card you can get, no drives and see if it will BOOT. Make sure the MB is not shorted out against the case. You don't want to introduce too many variables to a new installation all at once. If it doesn't work, it's difficult to tell where the problem lies.