I made the mistake this morning of using a micro SDHC card in the helmet camera which hadn't actually been pre-formatted by the camera itself. The result of this was that it didn't work :-( Nothing could be done about it for today's ride but I found the instructions to format it using the unit, which are not in the manual, here they are:
Unlike the Contour1080p and original ContourHD cameras, SD cards for the ContourGPS must be formatted with the formatting “pinhole” button on the camera. To format a microSD card, do the following:
1. Power off the camera.
2. Remove the microSD card from the camera.
3. Power up the camera with the microSD card removed. The camera will TRIPLE beep and the SD card LED on the lower rear of the camera will flash red and the front record LED will flash red/yellow, indicating the SD card is missing.
4. Leave the camera powered up and insert the microSD card.
5. Using a pin or small nail, push and hold down the pinhole "formatting" button located above the SD card slot. The camera will beep once when the format is complete.
6. Release the pinhole button only after the camera beeps.
7. Power off the camera by holding down the power button for 3-5 seconds.
8. Power up the camera. The camera should boot normally and be ready to shoot video.
All data on the SD card will be lost during the format process.
The other thing to do of course, which I didn't do, is to do a test recording before you go out with a new card, especially if it's something important. In the event it rained today and it was cloudy so nothing much was lost ;-)