First Build - No Beep No Screen No Boot

[Bluesummers]

This is my first build and I'm having trouble with several things such as the computer doesn't make any "beep" noises nor does any mouse/keyboard work (i've tested these components on another computer and they perform just fine). I also get no response to the monitor and there's just a black screen. The monitor works perfectly. I've taken out several pieces of hardware and put them back in to check if it was cable problems, but I get the same outcome. I'm pretty sure it's not a power problem because the PSU, CPU, Exhaust, and Intake fan all spin and light up perfectly. I can also hear the hardrive spin and the CD Drive opens and closes like it should. I'm not sure if it is a malfunctioned video card (because there is no onboard video) or if it's something else to do with jumpers or if the memory sticks don't work (even though I've placed them in the correct spots and replaced them countless times and have also checked that they are compatible with the motherboard). Any help would be greatly appreciated because this is driving me insane!! It looked really fun and interesting to build a computer, but I'm just having some trouble with starting everything up and troubleshooting some problems. Thanks! in advance. Below is the hardware I have used: THANKS! ANY HELP WOULD BE APPRECIATED




NZXT NEMESIS Black Steel ATX Mid Tower (Exhaust fan and Intake Fan)
ASUS A8N-SLI Premium Socket 939 NVIDIA nForce4 SLI ATX AMD Motherboard
XFX PVT70GUDF7 Geforce 7800GT 256MB GDDR3 PCI Express x16 Video Card
AMD Athlon 64 4000+ San Diego 1GHz FSB Socket 939 Processor
NEC Black IDE/ATAPI DVD Burner
ZALMAN CNPS9500 LED 92mm 2 Ball Blue LED Light Cooling Fan with Heatsink
---Arctic Silver 5 Thermal Compound
Antec TRUEPOWERII TPII-550 ATX12V 550W
CORSAIR XMS 1GB (2 x 512MB) 184-Pin DDR SDRAM DDR 400 (PC 3200) Unbuffered
Seagate Barracuda 7200.8 ST3250823AS 250GB 7200 RPM Serial ATA150 Hard Drive