working system now won't post.

this is my 4th build and the first one that actually worked the first time i powered it up. been working perfectly since christmas. i believe in the end the mobo may have gone but i don't know what else i can try so i will ask. i'm about to pull the trigger in the next week or so finally on a gpu and this would be my frekin luck. today i am going to pick up a new psu just in case ( i need one anyway) though i have tried a different one but it is older and only 275 watts and from an old optiplex which i am using right now. i also have already just a few minutes ago submitted a ticket to gb in case i need an rma to get the ball rolling

pc is as follows"

fx-6350 cpu
giabyte 78lmt-usb3 mobo
500 watt atx psu
2 x 4gb crucial ballistix ddr3 1333mhz ram
1 tb sata hdd
win 7 64-bit os
dvd rw but i don't have it connected unless i need it

system started acting wonky about 3 days ago with the sound crapping out after a few minutes. i took it out into the living room to crank up assassins creed 2 on the big tv ( i got it running pretty good with on board amd hd 3000) and thats when the sound started acting up. a reboot fixed it but only for about 20 minutes. powered down and made sure that moving it didn't unseat the audigy card. snug as a bug so i decided to power down again to remove it and go back to on board sound which is an atrocity compared to a thx sound card. the on board worked fine.

been using it as usual til about 2 hours ago. been going strong on assassins creed 2. on a side note the first one is horrible but how it ended i had to get the 2nd one which is actually pretty awesome. haven't finished the 2nd one yet so don't spoil it for me.

i decided to throw into safe mode to reinstall the sound card drivers since i love my audigy card even after almost 7 years now. it hanged at the welcome screen and went black no desktop.

another restart and now it won't post. all fans spin up and the hard drive does spin up but the hdd led doesn't light up either. i've tried leaving it running for a few minutes listening to see if windows does boot and give me sound indicating the on board graphics crapped out.

tried clearing the cmos. tried running either stick of ram in all 4 slots. tried another psu. tried running without the hard drive hooked up. tried taking the cpu out and powering it on.

i don't think its the bios. board has a dual bios that is supposed to kick in the back up automatically. i've never had a virus that messed with it but i am not ruling it out either that it could have messed up both. i've never had parts crap out this soon on me. only thing that ever did was a mobo but it was after 4 years.

oh and i pulled everything out of my case to rule out shorting . i don't have a test bench but i laid it out on the static bag that came with it and nothing.

i'm no expert but i am no stranger of not being able to get a setup to boot but i could always figure it out that this has me stumped.

if anyone can think of anything else i can try please give some input