I have a Flash Drive which shows only 1.46GB of space available on Mac OS X. It was having problems on Windows, so I ran an HP utility. (I can't find the original SU question)
What could be wrong and how can I fix this?
I found out why this is. I needed to delete the Trash, form my Mac, not just "Move files to Trash".
When you delete something on a USB stick on Mac, it just moves it into a folder on the USB stick called ".Trash". When you are using it with multiple Macs, it moves the files to a ".Trashes" folder.
Emptying the trash on my Mac solved the problem.