FWIW I assure you that your CarPC won't boot when it is below freezing at least until the drive has warmed up to approx 0 degrees. A constant freezing/heating of the "fluid liquid bearings" will likely cause the HD to fail quickly.
For me, part of the justification of having a CarPC is having 100% uptime just like a regular CD player would. This won't be possible with a HD based PC in freezing temperatures.
If you do go the CF route, you don't have to "swap" drives ever - you just plug in your portable media drive to a USB cable that you have extending from the PC in the trunk to the front console area. The CF card stays installed in the PC in the trunk. Think of plugging the portable media drive in as putting a CD in whenever you get in the car
Of course in the warmer months this means that you just leave the media drive plugged in full-time if you want. Another advantage to this type of install is that you can easily take all your media inside to synch/update.
I am actually a Sociology major...so, social engineering?
