Before I start just let me say I'll be testing everything with my multimeter before plugging it in and I won't be alone when I try it out.

I'm building a hot wire foam cutter power supply, it's basicaly a light dimmer switch attached to a 25v DC transformer. Here are the plans

Instead of just cutting the end off of an extension cord and wiring it into the unti, I took the female power plug out of a computer PSU. It appears as if there's some sort of resistor across the prongs on it's backside, what's it there for? Should I remove it?

It's there to help against surges and with grounding. I'd suggest you use an extension cord instead of a female plug from a PSU.

I kind of thought that's why it was there. If it's going to cause problems I can just unsolder the resistor

It won't hurt it to leave it there. I'm sure you're using the female port so you can easily remove the power cord if necessary... I like those ports also [img]/images/graemlins/smile.gif[/img]
Make sure you cover the backside though... I made the mistake recently of not doing so and I not only shocked myself when I tried to unplug the device (cause I had it open and wasn't paying attention to where I put my fingers), but I also fried a bracelet that was lose and shorted across the terminals :O It burned some links straight out of it in a giant blue glow.