Erasing off a 2 TB external hard drive

[FinnTheHuman]

Hello,
I'm having trouble erasing things off my external hard drive. Some background info:
OS: Windows 7 Ultimate 64-bit with Service Pack 1
Laptop: HP Pavilion dv7, quad core, 6.00 GB RAM
External Hard Drive: 2 TB Eagle Consus model ET-CSTSU3-BK

My external is connected using a e-sata to USB 3 cable, and normal read/write works fine,
but when I try to erase a file, folder, or free space, it immediately fails and says "completed
with errors." Eraser works fine on my laptops internal hard drive.

Thanks in advance!
-Ben

EDIT: I ran Eraser as an administrator and it was able to erase files on my external, so I don't
have a pressing problem any more, but I am curious as to why I needed admin privileges to
erase things.
Thanks again
-Ben

 

[Joel]

Erasing unused space, for most people, do not require administrator rights. However, there are circumstances which do require this. As such, Eraser errs on the side of caution and only erases unused space if Administrator permissions are given.

 

[PatricioC]

I did what Joel recommended and work fine, I have twice the space, but truly you have to be careful because can erase useful data.