Some things to try:
1. Enable hidden Administrator then login to it and try to delete the file
Open a Elevated Command Prompt
Press WIN + X to open Start context menu.
Select Command Prompt (Admin).
Enter net user administrator /active:yes and press Enter
Type exit and press Enter to close the Command Prompt window.
Note: /active:no will disable it again.
Logoff then login as Administrator.
Try to delete the file.
2. Install
Unlocker and use it to delete the file.
3. Take Ownership of the file then delete it.
Easiest way to do this is to add the
Take ownership option to the right click Context menu.
See here:
Take Ownership Shortcut - Windows 7 Help Forums
Says for Windows 7 but works for Windows 8 too.
Once installed, right click on the file and choose
Take ownership then delete it.