Need Help...Can't Find A Solution

I recently bought parts to build a new computer...it is my first time...i am a computer building virgin

Anyways me and my friend hooked it up...my power supply was DOA..so i got a new one....then after i got that in...it turned on..but now nothing displays in my monitor.. so i thought it was my graphics card.. but we put my graphics card in my friends comp and it worked...so now it might be the motherboard?
My luck is really crummy

Here are my products:
CASE:
XION II XON-103 Black SECC Steel ATX Mid Tower Computer Case 450W Power Supply - Retail
http://www.newegg.com/Product/Prod [...] 6811208008

GRAPHICS CARD:
SAPPHIRE 100245L Radeon HD 4850 512MB 256-bit GDDR3 PCI Express 2.0 x16 HDCP Ready CrossFire Supported Video Card - Retail

POWER SUPPLY:
PC Power & Cooling S75QB 750W ATX12V / EPS12V SLI Certified CrossFire Ready 80 PLUS Certified Active PFC Power Supply compatible with core i7 - Retail
http://www.newegg.com/Product/Prod [...] 6817703009

Internal Harddrive:
Western Digital Caviar Black WD6401AALS 640GB 7200 RPM 32MB Cache SATA 3.0Gb/s 3.5" Internal Hard Drive - OEM
http://www.newegg.com/Product/Prod [...] 6822136319

MY FAIL MOTHERBOARD:
GIGABYTE GA-MA790X-UD4P AM3/AM2+/AM2 AMD 790X ATX AMD Motherboard - Retail
http://www.newegg.com/Product/Prod [...] 6813128387

DVD THINGY:
LITE-ON Black 18X DVD-ROM 48X CD-ROM IDE DVD-ROM Drive Model iHDP118-08 - Retail
http://www.newegg.com/Product/Prod [...] 6827106275

CPU:
AMD Athlon II X2 250 Regor 3.0GHz 2 x 1MB L2 Cache Socket AM3 65W Dual-Core Processor - Retail
http://www.newegg.com/Product/Prod [...] 6819103681

Memory:
G.SKILL 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 1066 (PC2 8500) Dual Channel Kit Desktop Memory Model F2-8500CL5D-4GBPK - Retail
http://www.newegg.com/Product/Prod [...] 6820231166

I do plan to upgrade more once i get more cash...if you need a reason for the over kill PSU

please help! sorry if this is in wrong forum

try resetting the cmos by shorting the 2 pins next to the motherboard battery for a couple seconds...see page 7 for location and page 33 of the manual for the instructions...good luck