Need to empty out my drive but get (error -50).

Hi Everyone!

I'm stumped and coming back for help.

1) I did a clean install of Yosemite to better my MBp's performance.

2) All went well, until I attempted to clean out my external HDD to further organize things.

3) Upon throwing anything into the trash, I get "The operation can’t be completed because an unexpected error occurred (error code -50)."

4) I changed permissions to READ and WRITE for everything in the INFO window.

5) I still can't alter anything.

Question:

How can I throw out unneeded files out of this drive to utilize space?

Additional information:

I used to use this drive as a Time Machine BU (But I am not attempting to throw out back ups, just other files).

Help appreciated.

Thanks!

M