I just resolved a problem that we have with Citrix clients and temporary licenses. The problem is that the Windows client machine gets a temporary license and then after 30 days the license expires and they lose access to the Citrix farm. The way around this is to go in and delete all of the subkeys in HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MSLicensing and then reboot the machine.
The problem that I had was that usually I will just walk over to the machine that has the temporary license and go into the registry as an administrator and delete the keys and reboot. In the case that I had this morning the machine was in a different building and was pretty locked down.
I was unable to remote onto the machine using RDP with any of the admin accounts that I knew which is really tough.
Finally I went to the c:\windows\system32 folder and right clicked regedt32 to runas another account, in this case an admin account and then connected in the file menu to the remote registry of the offending computer. This actually worked really well. I was able to delete the MSLicensing registry keys and have the user reboot (could have done that remotely as well I guess) and the machine is now as good as new