Hard drive free space is wrong?!

Hi! I'm having some problems with my external hard drive, please can someone help!

I have a 500GB external hard drive that is partitioned into 3 sections - [1] Mac OS extended for dedicated time machine backups (200GB), [2] Mac OS extended for general file storage (100GB) and [3] FAT32 for backing up my husband's windows PC (the rest). I've been doing some video editing and moving clips between the external HD and my macbook. But now I've finished I noticed that something weird has happened. The Mac partition of the external HD currently has only 3 files, around 1.2GB. But Finder is showing 77GB is used and therefore not letting me copy my DV footage (around 40GB) that I want to transfer to a friend's computer.

I've put a screenshot here - and have hidden files/folders displayed. So what is taking up the 76GB that finder says is used?!

thanks in advance for any help!
kate

 

Fixed now thanks to a twitter suggestion - emptied the trash can - duh!