Here’s something that I came across from the US Dept of Transportation regarding lithium batteries on airline flights. Starting Jan 1st, 2008 you can’t pack lithium batteries in your checked baggage. You can, however, carry lithium batteries on the plane in your unchecked bag. So if you plan to bring extra lithium batteries for your laptop, cell phone, or Pocket PC device you’ll need to carry it on the plane and not have it in checked baggage. I guess not having a replaceable battery for your Zune is a good thing in this case.
I normally carry an extra battery for my laptop and smartphone when I travel, but I keep them in my carry-on bag. It’s strange that you can’t have such batteries in checked bags but it’s ok for carry-ons. I guess the DOT is worried about batteries exploding or something, which obviously could happen in your carry-on bag as well. I wonder how many people know about this new rule?