Although this doesn't really answer your question about how to run a PC fan, it's still sorta relative to the topic.

I've heard of folks using those new Oust fans in their humidors without the fragrance packet. The fragrance packet comes sealed and therefore the fan will not taint your cigars.

Runs on a D cell battery and cycles on 5 minutes, off 15 minutes. I thought I heard somewhere that it would run for a couple months on one D cell battery.

http://www.oust.ca/en/fan.aspx