I recently upgraded from my overclocked Core 2 Duo to a overclocked Core 2 Quad. Unfortunately, the old stock heatsink couldn't keep up with the heat put out by the new CPU. An aftermarket heatsink was out of the question, due to the odd BTX mount and the fact that I am cheap To deal with the increased heat output, I decided to set up a water cooling loop. Unfortunately, BTX water blocks are as rare as hen's teeth. I decided that the best course of action was to make my own water block.
First, I took a stock Dimension 5150 heatsink and removed all the fins.

I made a quick design in Sketchup and attempted to CNC the block. Sadly, I broke all the milling bits and gave up
I ended up drilling a 1/2" hole for the inlet and outlet then drilled a grid of 1/4" holes. I then used my dremel to cut troughs connecting the drill hits. I topped the block with lexan and sealed it with silicone.

I then lapped the heatsink with 220 grit, then 320 then finished with 400 grit.

My coolant reservoir is an old Jif peanut butter jar (no shame ) with a cheap 12v submersible pump in it.

The pump line goes to the water block and over the CPU.

The water then goes to a 120mm radiator that I got from a broken Corsair H50.

The line then returns to the reservoir. The block works really well, the CPU doesn't get over 40 degrees at max load. It looks bad, but it works!

That is really cool. I would be worried about it leaking but I am a worry wart about that stuff. but still awesome

only thought why not replace the water with some kind of non conductive coolant? It is not that expensive and may save your rig one day

Non-conductive coolants are expensive and don't stay non-conductive for long. I'm using distilled water which is non-conductive, at least for now

I too would be exceptionally worried about leaks. Did you do some bubble-testing before you mounted it onto the expensive electronics? This is really impressive work; great job!

I ran it in a closed loop in my sink for three days straight and checked for leaks before installing! I would only be worried about the graphics card though, everything else was free