you need to check out the partitioning; use sfdisk or similar on the tablet, or whatever Vista has.

the tablet file manager will only see the first partition, I believe, and the partition type should be something sensible, either vfat or linux.

if you can, I would use "sfdisk -l" on the tablet to check that it's sensible, and if not, use sfdisk to make it so, then put a filesystem on it with either mkdosfs (for vfat) or mke2fs for ext2.