There is a quick and easy way to check which Domain Controller your windows PC is authenticated to via the command line.
Click Start and enter CMD (Windows Vista/7/2008) or Start → Run → CMD (Windows XP/2003)
When the CMD window opens, enter the following and hit enter:
echo %logonserver%
or alternatively use the following command and hit enter:
set L
You can also use the following command to get more information.
nltest /DSGETDC: