I feel I must add, that while the Hard drive upgrade guide says 19.5mm... this was in a recent email from David concerning my player:

"It looks like the large 5GB drive in the player was too heavy and put extra weight on the connector when the player fell.

I also noticed that the drive touches the lid of the player - this may reduce the effectiveness of the shock mounts."

I don't have the exact measurements of the drive. But it appeared to be double the size of the 9.5mm 30GB Fujitsu drive. Again, I am not positive on the height of the drive. Just as a warning. But I did have it running very well for 6+ months, until I dropped my precious. But it was the drop that caused the damage.