Oh my... well you can ignore the disk space part of the post. I got my cards confused, and it's actually a 32 GB card. And they play the marketing game where they say GB = 1,000,000 bytes instead of 1,048,576 bytes, so it's really about 30.5 GB. Take away 6GB for the data partition, and give up some overhead for formatting, and the reported size of the second partition sounds right.
So sorry for the confusion, it sure helps to actually look at the writing on the card! (I had it confused with some 8GB USB sticks I bought at the same time...) How embarrassing, I feel like such an idiot... :-[
That still leaves the issue of not being accessible to Windows. The only other card I have at the moment is a 4GB card with some system critical data on it, and I'm hesitant to re-format it at the moment. But I will keep playing with it and see if I can figure anything out.
Thanks for the help, and sorry for the misleading information!