OK. What is your version of Windows, Home or Pro?
In pro version, right click on the file/directory -> Security
Click Advanced button
There you click the Owner link on the top and take it to yourself (whatever is your user name in the windows)
Next you click on "Change permissions" at the bottom and add "Everyone" then tick Full Control for it. At that point you would be able to do anything with the file.
If you have Windows Home than the story is different, most likely you will not have the nice GUI window to change this but most likely the command icacls will work from Administrator command prompt. I'm lazy to read the manual how to use the icacls, just let me know if the GUI version works for you
I did an example screens pointing on VirtualBox drivers.
EDIT:
It may be even simpler if you boot in safe mode (you already know how to invoke the special boot menu to bypass driver signing, it's number 3 or 4 on the list), don't remember for sure though, just think that in safe mode you are kind of 'absolute administrator' so you would be able do delete anything without bothering with the permissions...