Deleting unused space requiring admin access


New Member
I have been trying to delete the unused space on my C: which is the main partition on my computer. Every time i try using eraser to delete the unused space it is coming up with errors and the task log mentions that could not delete and to try running as administrator.

I have checked twice that I am the administrator on the computer and there is no other user set up. Also I have right clicked eraser and selected 'run as administrator' but this has not worked either. I am using Windows 7 Home.

How can I run the unused space eraser correctly?
If windows settings need to be changed, could you please advise which settings I need to change. Thanks