Trash won't empty

My external is getting pretty full and was trying to delete some previous backups. I put them in the trash and each time I try to delete them I get error code 8003. I tried using Trash it! but after 12 hours of letting it run nothing was removed.
Any ideas of how to empty it?
After carelessly playing with terminal (learned my lesson) I just would like to put the back up files back on my external, which says "can't be done since backup items can't be modified"

Thanks