Fans spin only for a split second

I have just finished first ever computer build. it consists of
An asrock 780a sli x3 motherboard
an nzxt tempest case
4gb patriot 2x2gb extreme performance 1066 5-5-5-15 ram
a corsair tx 750 watt power supply
gtx 260 evga (192 version)
an old seagate 160gb ide hardrive
and an old samsung cd drive
oh and almost forgot the phenom 2 920

All was going well in my build till i tried to power it up and all that happened was the lights from the fans went on and then spinned a spilt second. I have actually already replaced the original power supply which was a cheapo old apevia 500w . I also bought a psu tester and the new corsair is tested and works perfectly. I also went out and bought the gtx 260 after i realized the asrock had onboard video but only did geforce boost which i found out can help a discrtete card but wont work standalone. Does anyone know of why this is not working its not giving me any post codes either so i pretty much have no signals indicating anything as dead but i could just be overlooking something. Any suggestions are appreciated.