Upgraded motherboard, pc turns on..but no signal on my display?

[gproefficient]

I upgraded m y old D945GCL motherboard to a Asus p5G41T MLX plus motherboard. I also upgraded to 4GB DDR3 -1333 RAM and got the Intel Core 2 Duo E6550-1333FSB @ 2.33GHz and a 500 ATX PSU with 6pin pcie connector and 12V @25
I turned off my pc, Put everything in were it should be and turn it on. The pc turned on, but there was no signal. the vga was in correctly everyhing was were it should be I checked. after 3 times of trying, I turned pc on again but t his time with my graphics card i n, and it didnt turn on at all. even when I took it out. so then I p ut all my old parts in, everything BUT the psu and everything works like nothing ever happend. whats going on?? was there anything I needed to do before I started putting the parts in? did I need to uninstall devices on this motherboard or what? I have windows 7 ultimate and I want to do a fresh install..but I really dont know what I need to do bfore putting the parts in..i dont know what to uninstall etc or delete. much help would be aprreicated..I really need help.

 

[o1die]

Try using a breadboard or cardboard box and test the board out of the case first. Use just the cpu/heatsink, onboard video, one or two sticks of ram, and the keyboard. Pull the power supply out of the case if the cables won't reach. You may also remove the board battery for a few seconds and replace (with the power supply unplugged) to reset the bios. Normally, when all connections are good, either the fans will turn or a light on the board will light up when you plug in the power supply leads. Also, rarely, the cmos jumper if in the off position to conserve the battery, but you don't want to power up the system with this jumper in the wrong position. The correct position is usually called "run" in the board manual. Once everything is connected and the power supply toggle switch is in the "on" position, you simply move a plain screwdriver around the case connector pins on the board until the board fires up. Don't worry about shorts; all these pins are low voltage. Been doing this for twenty years, so it works.