vista 64 problem

i just built a new computer and installed vista utimate 64 bit but my computer keeps crashing all my hardware it capatible with it any ideas on how to fix it?

i have a nvidea 9600 gt

4 gb memory

n force 790i ultra sli

950 watts power supply

and the crashes are ramdom sometimes while the system is turning on and other times while your playing or doing stuff on i t

help please