How to reset the admin password and side effects on a windows 2008 DC?

I have 2 problems - my local admin password is not working at all - it was probably incorrectly typed twice. I only have one domain admin account setup and the password i have written down for it is no longer working (i've also tried every single password it's been set to previously).

An added complication is that the server was running a trial version of sbs 2008 which has now expired.

The server i need to gain access to manages all AD roles, I have access to the hyper-v host that the server is running on, as well as access to a member server (which is used for terminal services only - it doesn't do anything in regard to AD)

I am aware that there are tools available to do an offline password reset on the local admin account. I've done this in the past to windows XP machines and know that one side effect is that it invalidates keys for EFS encryption on the account you reset. If i do this on a DC are there any side effects that i need to be aware of?

Currently my only plan of attack is offline reset the local admin password then use that to do an online password reset on my domain admin account - will this work?

Or can someone suggest a better plan of attack?

Thanks :)