The Stuff

The plan is to submerge my computer in mineral oil as a cooling medium.  Mineral oil has a substantial heat capacity compared to air, and the heat will be removed from the system by natural heat loss from the case sides and (mostly, I would guess) by pumping it though a radiator outside the case.

The case.  The plan is to build a sturdy waterproof (oil proof) case out of 3/8" acrylic.  Most of the components will be attached to a tray that slides down into the case, with the motherboard positioned in such a way that its i/o ports will be just out of the oil (to avoid oil wicking up the cables).  The hdd will, of course, be kept outside the oil.  I have heard of people sealing their hdd's and successfully submerging them that way and I may eventually come to that, but for now I want to go with simplicity.

The stuff in the case.  It is about 1-2 years old, but still has some of life left in it.

cpu: AMD Phenom II X2 555 Callisto 3.2GHz DualCore
motherboard:  ASRock M3A770DE Socket AM3 AMD 770 ATX Motherboard
hdd:  WD Caviar 640GB 16MB 3.5 3.0Gb/s SATA
gpu:  MSI RADEON HD 4890
ram:  4GB (2x2) DDR3 1600mhz
psu:  Antec BP550 Plus 550W

The motherboard will be replaced with a Biostar A780L3B, partly because it has all solid state capacitors (non solid state caps and mineral oil don't mix) and partly because it is a good few inches smaller, which allows a smaller case, less acrylic used, less oil, and less money.  Everything else should be good to go.

Ordered the Acrylic at a decent price on ebay, even considering the shipping charges.

Also waiting for arrival of:
1x Swiftech MCP655 12 VDC Pump
2x Converted heatercores for radiators from Danger Den
10ft of 1/2" tubing and clamps

Haven't got the mineral oil yet, waiting to see exactly how big my case is going to be first.

Expect pictures as things start to come in.