If you look at the label for you PSU it states the 12volt rail is only good for 16 amps.
12volts x 16amps =192 watts of 12volt power.
The Core 2 is a 65 watt part.
The GTS450 is a 110 watt part.
That puts you at 175 watts on the 12 volt rail.
It’s very close but it should be ok.
This PSU is a good example of a poorly labeled model. It’s labeled as 400watts but it only puts out 192 watts of good 12 volt power.
It also puts out 208 watts of 3-5volt power. Who could ever use 200 watts worth of drives, fans and USB devices?