Applying AD group membership changes for computer account(s) without a reboot required? Use klist.exe (Kerberos List) which is part of the Windows 2003 Resource Kit tools. Install the resource toolkit and copy klist.exe to the appropriate computer.
Start a CMD-box in elevated rights after the computer account is added to the appropriate AD security group and use the following command to purge kerberos ticket on the affected computer:
As simple as that…