Power loss. Hi my computer is shuting off when windows loads and if i start right back up then it

Question

Hi my computer is shuting off when windows loads and if i start right back up then it might shutoff before it gets to windows or it loads windows and shuts off again . Tech people from alienware told me it was a power supply issue so i put a new power supply in and i still have the same problem.

i have a Foxconn nforce 590 sli motherboard
D-Athlon 64 x2 5600+ am2
nvidia geforce 8800gts 320 mb

now on the motherboard when it is just pluged in and not on there are 2 amber lights when i turn it on 2 green lights come on right next to them then under that and to the left there is 2 led letters FF lit up.

please help !!