Hello All,
After installing Snow Leopard, I was experiencing the fan running constantly @ 6200 RPM on my black MacBook. I did the PRAM and NVRAM resetas suggested on this board and via apple supportbut this didn't correct the problem. I spent 2 hours on stand-by at the Genius Bar, and their best suggestion was to reload Leopard if the constant fan running was a problem for me. 
As one last-ditch effort, I installed the 
iStatPro Widget, which showed something called 
"FP-Injector (707)" using 99% of my CPU. I couldn't find anything about this online, but eventually I tracked the parent application down to 
FinderPop. I went to the 
finderpop.com website, and in big letters across the top it reads: 
FinderPop 2.2 is not compatible with Snow Leopard 10.6. 
I uninstalled 
FinderPop (from the Preferences Pane), and now Snow Leopard is running cool and quiet

 I hope this info is useful to someone out there.