Hive: HKEY_LOCAL_MACHINE
Key: Software\Microsoft\Windows\CurrentVersion\Policies\System Name: LocalAccountTokenFilterPolicy Data Type: REG_DWORD
Value: 1
Please be aware that this is a security hole if your systems are not patched (Not to mention zero day attacks). Use with discretion and without blame (Me that is).
From Microsoft:
How UAC remote restrictions work
To better protect those users who are members of the local Administrators group, we implement UAC restrictions on the network. This mechanism helps prevent against "loopback" attacks. This mechanism also helps prevent local malicious software from running remotely with administrative rights.
Source: http://support.microsoft.com/kb/951016/
Other Source: http://en.wikipedia.org/wiki/Administrative_share