Be careful using the neuros/microdrive with a helmet cam.
We corrupted our microdrive.
Go with a 2GB CF.
By the way, a cheap 5 volt regulator and a 7.2 volt RC battery works like a charm. We made our own system.
5 volt regulator here:
http://www.eaelec.com/12to6.htm#5voltWeatherproof cam/audio that runs 3 hours on a 9 volt battery.
We used our neuros at -17C in the snow with an all weather headcam (snowboarding).
Works great!
Ex-Navy