Deleting an in.progress file from Finder

I was backing up my computer through Time Machine to an external hard drive, but had to stop the backup. This left an in.progress file on my external hard drive, which I unthinkingly moved to the trash. Now, I am having an impossible time trying to delete it permanently. First, when I attempted to empty the trash it kept freezing at 18 files. When I tried secure empty trash it counted files forever. I attempted several commands in the Terminal and held down the option key while emptying the trash with no luck.

Finally, I went in and changed the the permissions of the file itself to read & write. Now, when I go to empty the trash it keeps saying that 501 cannot be deleted because it is in progress or in use. Any attempts to change the permissions back result in an 8076 error message. Is there anything else I can try? I have other files in the trash that I really need to delete in order to clear up space on my hard drive and I have several hundgred GBs of pictures, video, music, and other documents on my hard drive so formatting it is not something I want to do.

Thanks,

C.