Hello all,
Well I was talking to a lot of people including SirPoonga, HowardC, and Oscar, and they all seemed to agree it would be totally fine to grab the +5v and ground for a trackball from a USB mouse's usb cord input instead of hacking out to another source such as the computer's power supply.
I finally did this, double checked my wiring, and plugged it in to try it. The computer says it's searching for an Unknown USB device, then nothing. Absolute nothingness from the trackball, the mouse buttons don't even work. So I unplug it, thinking it's a failure, and I try to plug in another USB device into the port, and nothing again.
So in conclusion, by trying to grab the power from the USB cable on the mouse, somehow it shorted out my USB port, and I would not suggest anyone to try this themselves. Maybe there was a reason no one else had tried this before me...
-CthulhuLuke
ps: although its a shame I'm down one USB port, the plus side is I might be able to convince my parents to upgrade this computer to a 1.4ghz AMD, cause I'll just swap out the motherboard, and leave everything else in place.