The demonstration you saw might have used a 3M product called Fluorinert. It
comes in several formulations, and the Parallax Technology, Inc. website has
a product information sheet on the FC-77 "electronic liquid" product.
"The inertness of Fluorinert liquid FC-77 permits its use as a direct contact
single and two-phase coolant in supercomputers ..."
At $100 to $500 a gallon, depending on quantity, it doesn't appear that this
will meet your "inexpensive" requirements.
Before I go any further, I should point out that what you are suggesting is
potentially a very dangerous experiment, as this deals with electricity and
That said, there are several low cost alternatives to Fluorinert, one which
might be surprising, and that is water. Not tap water though, but rather
distilled water will do the job. Problem is corrosion, so scratch that.
Next we have cooking oil. That's right, off the shelf vegetable oil, such
as corn oil, etc. This Tom's Hardware article titled "Strip Out The Fans,
Add 8 Gallons of Cooking Oil" by Frank Völkel covers the process in great
detail. Must reading for such a project.
"... not only did we find that our AMD Athlon FX-55 and GeForce 6800 Ultra
equipped system didn't short out when we filled the sealed shut PC case with
cooking oil - but the non-conductive properties of the liquid coupled created
a totally cool and quiet high-end PC, devoid of the noise pollution of fans."
Cooking oil appears to be the least expensive route to go, if we exclude the
use of the corrosive distilled water, but vegetable oils can turn rancid and
can get "gunky" so what others have done is to use mineral oil instead, which
runs well under $10.00 a gallon. Make sure it is 100% pure mineral oil.
This has been covered by no less than the Wall Street Journal.
"Sounds of Silencers Are Loud and Clear: PCs Are Too Noisy"
This MacAddict forums covers other alternatives, such as polyalphaolefin.
To go full circle, if you could clear up a few extra dollars, you could go
with "recycled" Fluorinert, referred to as reclaimed perfluorooctane, at
under $20.00 a gallon, as pointed out on this bit-tech.net forum posting.
"... we do sell PF 5080. However we sell it as reclaimed Perfluorooctane."
The above referenced company is TMC Industries, Inc.
If you attempt this project, keep in mind that hard drives are "moving parts"
as well, so you will want to keep it out of the "bath" as well.
If you need any clarification, please feel free to ask.
Google search on: nonconductive liquid
Google search on: Fluorinert
Google search on: "mineral oil" PC
Looking Forward, denco-ga - Google Answers Researcher