new system build problems

ok so i have started to build a computer for the first time and i feel like i knew enough to get it working properly so here it goes
my parts are:
evga 780i motherboard
evga 8800gts 512mb
oc power and cooling 750w power supply
thermaltake ultra cpu fan
antec 900 case
2x2gb g.skill memory
2x lg dvd drives
q6600 proccessor, arctic silver thermal paste

So first time i built it all put all inside case turned it on everything looked fine, all fans were running video card fan cpu fan, dvd drives turned on and worked properly everything looked good. Then i hear 3 beeps and the monitor shows nothing on the screen, it seems like the monitor never turned on it was in power save mode. So i unassembled evertything and did the bare bones setup taking the motherboard out and having one stick of ram the cpu and the videocard turned it on, did the three beeps and had error 6f and 7f on the motherboard talked with evga they say its videocard or motherboard problem. So i switch out the videocard with my other computer an 8800gt and i use the barebones setup and it boots up to bios and such, i then proceed to hook up the hard drive and other stick of ram and seems fine then i hook in the dcd drives and it does the three beeps again and shows nothing, i then just took it out the dvd drive and expected it to still boot to bios and it does the 3 beeps again and shows nothing still getting the 7f error through out im just able to get into bios with the 8800gt, im not sure what could be the problem any help would be appreciated thanks

It should be the other way around: build the barebone & make sure it works before putting it in the case.

Things I'd do:

- unplug power cord, press front power button, remove cmos battery, short jumpers to clear cmos, wait for 1 min, hook everything back up.

- triple-check all connections.

- try each stick of ram in each of the slots, starting from the furtherest slot. That would be 8 tries. Once the pc posts, set up ram settings to specs in bios. Do not swap ram while the mobo lights are on. Unplug power cord, wait til they're off. Or you may damage the board and/or ram.

If that doesn't fix it, ask these guys:

http://www.evga.com/community/mess [...] aultmb.asp