windows 2008 R2 add another local administrator account without knowing administrator password

windows 2008 R2 add another local administrator account without knowing
administrator password

I have physical access to a windows 2008 R2 server, I am trying to add a
second local administrator account without knowing the original
administrator password. It's important that the original Administrator
password remains untouched, booting from a livecd is feasable. Is there a
way to do this?