970 PRO3 and no video input

hello guys recently i bought asrock 970 pro3 and it seems i've encountered issues :

1. the pc will start but my gpu turns into full speed and won't go down and occasionally spins at a normal speed but still got no video on my screen (both cases lit the 3 LEDs out of 4 in my video card)
2. as soon as the pc starts, i can't turn off the pc (power button won't work,no loading activity LED and reset switch stop working too)

strangely, the night my mobo arrived it starts normally and boots into bios or enters windows repair screen (which tells me i have to re-install my OS). the net day i tried to install the OS it won't boot normal as the other night.and now, 2 points above always occurs whenever i tried to use my new mobo...

i tried RMA the items and they tested at the store it went fine,but again...when i tried at my home,it won't start again...all of the cables are connected perfectly and i double checked it...

ooh and one other thing,there's no "beep" sounds at all when i thought there's something wrong with my ram...

my specs are:
amd phenom 2 x4 945 @default clock
patriot 8GB ddr3
hd his 4890 turbo 1gb
asrock 970 pro3
int. hdd wd 320gb
ext. hdd wd 2t

please help me figured out what exactly went wrong along the way..and thanks guys