If you have a partition mounted in a folder (like C:\Video) instead of using a drive letter to access the partition, the free space calculation looks at the space remaining in the C:\ drive, instead of in the mounted partition.

The work-around, obviously, is to access the partition through a drive letter.

Don't know if this falls in the realm of a bug or a feature. Just mentioning so Sony can decide to look into it if they want.

David