Help! 7800GT broken?

I have just recently purchased a new computor and I am building it for the first time. At first my problem was the CPU and I found out that there was not enought power for it, solved that. Now my problem is that my new ASUS Geforce 7800GT PCI Express x16 Video Card will not send a signal to my monitor. I have tried different PCI Express x16 slot for it (same result). I have tried using both of my single stick of 512mb at one time to see if one of them was bad because I found a forum that said that might be the problem (same result). I have my video card plugged in and securely placed on the motherboard. At this point anyone’s idea I will try and any that I get will be most apperciated. Below is the hardware that I purchased:

VIKING 1GB (2 x 512MB) 184-Pin DDR SDRAM Unbuffered DDR 400 (PC 3200) System Memory - Retail

ASUS EN7800GT/2DHTV/256M Geforce 7800GT 256MB 256-bit GDDR3 VIVO PCI Express x16 Video Card - Retail

AMD Athlon 64 X2 4200+ Manchester 1GHz FSB 2 x 512KB L2 Cache Socket 939 Dual Core Processor - Retail

ASUS A8N-SLI Premium Socket 939 NVIDIA nForce4 SLI ATX AMD Motherboard - Retail

Western Digital Caviar SE WD2000JB 200GB 7200 RPM 8MB Cache IDE Ultra ATA100 Hard Drive - OEM

ASUS Black 16X DVD+R 8X DVD+RW 8X DVD+R DL 16X DVD-R 6X DVD-RW 16X DVD-ROM 40X CD-R 32X CD-RW 40X CD-ROM 5X DVD-RAM Read 2M Cache IDE DVD Burner - OEM

Antec TruePower 2.0 550 Watt Power Supply

                                                         Thank you,
                                                                Jeffrey