PC Shutdown

Windows 7
Intel i5 5470
Asus mobo P8Z77-V
RAM 4gb
PSU 450w
Gigabyte GTX650 ti Boost 2gb

I recently installed this new card and when I run a game it shuts down the PC, which then reboots. Does the same on various games. When I install old Nvidia 9600GT no problem playing the same games. Nvidia CS could offer no help after changing settings and re installing drivers. All plugs are in and tried the card on different psi slots. All temps are fine and the card passed an online performance test.

Please assist

DrNoNo