Hi Leo Swart
Some ways to get back administrator access:
Are there any important data inside your PC? else if it fails, consider getting a live linux GUI CD to access your data.
Are they are Microsoft Windows 7 COA (Would like to check if the label is still intact and product key is visible) You need it later for Windows 10 fresh installation.
IMO I would prefer a fresh install of Windows 10 than a upgrade from windows 7.
As from experiences, some software and stuffs can mess them up.
Before you consider to do a clean installations, there are a couple of stuffs you need to do.
Get a thumbdrive, 8GB or larger.
Download windows 10 installer x64 from another pc with internet access.
Make the Win10 1803 USB
Boot up to your Lenovo BIOS page
Start PC and press F2 (Some might need to Press Fn + F2) to access
Set to Boot to OS Default, Enable secure boot.
Boot up the USB (F12 Boot Menu) (Some might need to Press Fn + F12) to invoke boot menu
Allow the installer to load.
If prompt for windows key, key in the Windows 7 COA into it, else if it is windows 8 sticker on your laptop, if it mention pro, select pro installation, else Home installation.
do a clean format, delete all partition and recreate again.
Remember to Update your laptop to the latest BIOS