A guest account is an account for users who don't have a permanent account on your computer or domain. It allows people to use your computer without having access to your personal files. People using the guest account can't install software or hardware, change settings, or create a password.

I don't know how you were able to turn an existing account into a guest account, so I'll give you some options on ways you may be able to access the administrators rights.

What access does the 'Other User' account have. Can you log in to that user and change the user accounts in the control panel?

Or you can try to change it to the admin account. Click on start menu, right click
on Computer, Click on manage. Go to Local use and groups -> Users. Right
click on Guest -> properties
Click the second tab "Member of". Click on Add. Add the Administrators group
to the guest account. Click ok.

Or enabe the administrator account at log on screen.
If you can access the administrative tools, right click on Local Security Policy, and run as administrator