Power supply

while looking into supopying my Gen6 with power I wondered if the Cables supplying Power to the HDDs of the computer carry the right voltage.
In fact they do. So if you need power fast and dont want to cut any cables on you PSU get a Y-shaped cable, cut of the unneeded cables (you only need yellow and black) and you are ready to go, Just connect instead of a HDD.
the Molex 8981 connector used there is rated for 30A per pin, so the 5 A of the Reprap should not be of any concern.
Combine that with a switch and a nice printed board at the back of your PC and you can supply your RepRap from the PC you are sunning the Software on

Most people run their Rep(St)Raps off of computer power supplies.

I wouldn't recommend using a PSU still running a PC to do it though. PCs are susceptible to noise, and a reprap may generate enough to cause problems. Also, if its not a custom built PC then it probably has the cheapest possible PSU that will run the computer, and you might not have 50W to spare. Better to pick up a cheap ATX PSU.

Even if you pick one up to use only with the reprap yor at least do not need to cut any wire connected to it.
Regarding Interference: It might be, but I have not noticed any problem with my system at least. i use a VIA C3 on a mini ITX board. currently there is no case at all, because I want to integrate it into my repstrap frame with some printed parts that i can only print when the system is up and running completely. So far I have tested X/Y movement at different speeds, the z axis is hooked up already, but lacks the belt so far. the Extruder however ist still work in progress. I will definitely report back if I ran into any problems.