Sometimes, being an Administrator just isn't enough. In that case, try being the SYSTEM account... You can run processes as the local SYSTEM account quite easily with PsExec (64-bit).
Use it as follows:
psexec -i -s cmd.exe
The command above would run a command prompt as the SYSTEM account. You can replace cmd.exe with something else, although from a command prompt, you can basically run anything else, all as the SYSTEM account.