Vista error: “The specified print monitor is unknown”

While installing network printer in Vista if you come across following error

User Access Control (UAC) is disabled, you cannot install print drivers from a remote server. To the solution is to re-enable UAC

For enabling UAC


Control Panel--Click on User accounts--Then tick on UAC

or
in Run type the command

C:\Windows\System32\cmd.exe /k %windir%\System32\reg.exe ADD HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System /v EnableLUA /t REG_DWORD /d 1 /f


For disabling UAC 

C:\Windows\System32\cmd.exe /k %windir%\System32\reg.exe ADD HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System /v EnableLUA /t REG_DWORD /d 0 /f