Could not read my external drive for making a time machine copy

[assipattle]

Hi

Today i tried to make a time machine copy with my external drive, btu while I was doing it, the system said my drive only had 20GB left and needed at least 130 . The thing is that my esternal drive is 400GB but when i connected to the my laptop I could only see the last copy I had made. I deleted the copy , but still it said I only had 20GB, so why couldnt I see any files in the drive??.
At the end I had to format my hard drive again, but I dont know what happened?? and would there be other way to open my drive and see what was in it??
Cause when i plug it into a PC it didnt even read it!!

Hope you could help me
Thanks

[ElDiabloConCaca]

When you deleted some items, did you empty the Trash?

[assipattle]

Do you mean the trash of my computer?? hmmm no i did not, i deleated everything that i could see from my hard drive , tne unpluged it, and pluged it again but still said i had only 20GB left.

[ElDiabloConCaca]

If you dragged and dropped files you wanted to delete into the Trash, then you must also empty the trash in order to actually delete those files and free up the space on the drive.

Dragging files to the trash is only half of the procedure for permanently removing them from the drive and freeing up the space.