Can I just strangle my mother, now?

So.  The story is this: my mother had an XP desktop tower.  It's an e-machine, from fourteen years ago.  It isn't a capable machine for really anything.  Useless. 

I got a refurbished Windows 7 tower.  I initially ordered it for my sister.  My aunt got my sister a Windows 8 machine (which she hates, but won't let us download the Windows 7 shell for), so the tower went to my mother. 

My mother discovered that the people who refurbished it didn't wipe the hard drive from what the previous user left, so the hard drive is full.  And it won't let her delete anything, says she doesn't have the authority to do so.

I was going to order a reboot disk to just reformat the drive without removing the OS.  I had it figured out, and Odysseus thought he might be able to fix it even without that.  So I called Mom to tell her to bring the tower on Thursday when they come to visit. 

In a long-suffering tone of voice, she said she was planning to, and we could keep it, and maybe give it to TinCan Assassin, and she'd just take her old, useless, piece of shit home with her. 

I give up.