I recently built a HTPC iut of old, outdated, junk parts however I was having serious overheating problems. I got the mobo and cpu as a combo and I didn't bother removing the heatsink. A, due to not thinking there'd be an issue, and B, due to me not actually having any thermal paste to reseat the processor. I decided to pull the heatsink only to notice that there never was any paste on the cpu! So I experimented using ILSCO De-Ox, a substance that I use at work as an electrician for a completely different purpose, instead of proper thermal paste. Lo and behold, it actually keeps my Athlon X2 6400+ (awfully antiquated, i know) from overheating and becoming unstable. Apparently the stuff is used as a thermal compound for applying heatsinks to SCR's, but I don't do that kind of stuff in my line of work.
It seems to work in a pinch but I don't know if I can downright recommend the stuff.