New Graphics Card Problem

Heya everybody,

Not too long ago I ordered a Msi Radeon HD 6670 DDR5, and when I install it into my computer, my monitor receives no signal.

I plugged the vga chord into the graphics card, I tried re installing it, I tried switching monitors.
Nothing.

I don't hear the normal boot-up when I turn on the computer either, so I doubt it's the monitor's problem. Many other people have had this problem before I know, but I suspect it could be my rather weak power supply in my computer.

Specs:

Windows 8 x64 bit

4gb of DDR2 RAM

Dual Intel Pentium CPU G645 2.90 GHz

Integrated Intel(R) HD Graphics

250w psu


I've tried installing the drivers for the 6670 and disabled the Intel Graphics to no avail.
So I might suspect that it could be my psu giving out(?) but I hear no sparks or red flags from the hard drive. But i've also read stories that the 6670 can run on 250w psu's, so i'm not sure.

I just wanna make sure what the problem is before I go out to buy a new psu. If you need more specs let me know.

Thanks!