VNC

Query current password:

PsExec.exe \\machine REG QUERY HKLM\Software\TightVNC\Server  /v Password

Set password for agent control:

PsExec.exe \\machine REG ADD HKLM\Software\TightVNC\Server /v ControlPassword /t REG_BINARY /d xxx

Set password for remote access:

PsExec.exe \\machine REG ADD HKLM\Software\TightVNC\Server /v Password /t REG_BINARY /d xxx

The password is encoded, Google VNC Password Encoder/Decoder