My computer has no admin user In system preferences, under users, standard is written under my name and there is no admin.

When i try to change preferences it asks for admin name and password to unlock it but my login password doesn't work as I'm not an admin.
Boot into single user mode.

Delete the file /var/db/.AppleSetupDone and then type exit and press return

At that point, the system will boot back to the normal setup process (keeping your old users intact) You will be guided through the steps to create a new admin user so pick a short name that doesn't exist on the Mac and you can then re-grant your normal user admin rights if you wish.