Franken-mac-mini - Spare internal 12v power line

I've got an '07 mac mini and I've upgraded the ram to 4GB, the HDD to an SSD, and the processor to the t7600 2.33ghz. My next project is to upgrade the lousy integrated graphics. I'm looking to siphon about 2 amps of 12v power from somewhere internally to power a gt710 gpu which is connected to the mini pcie slot via an adapter. i really don't want to run another power cable into the chassis so i'm hoping that someone will know where i can tap in to a 12v line. i'd prefer not to solder, but if that's the only way i can deal with it.

i plan on removing the optical drive which should give me JUST enough space to cram the gpu in. I was hoping that without that there'd be enough spare power to run the 25 watt gpu.

I figured powering it internally would be difficult considering g it only has a 125w psu, but thought this would be the place to ask.

I do actually have it all hooked up externally right now, I've gotten it to display the Windows 7 logo/splash screen via the external gpu, but then it goes to black screen. Same when I boot in safe mode. I don't understand why it lets me use the external gpu to start to boot into Windows or select safe mode, but fails to complete the boot.