During a PXE installation of Windows Server 2008 R2, if PXE user authentication fails, check that the system date and time are set correctly. If the systems date and time is incorrect, PXE authentication fails, and the network installation of Windows Server 2008 R2 does not happen.
Workaround
Use the system BIOS to set the system date and time.
Reboot or power on the server.
POST messages appear, and prompt you to press the F2 key.
Press the F2 key.
The BIOS Setup Utility main menu appears.
Use the left and right arrow keys or the Tab key to navigate through the top level of the utility.
Use the up and down arrows to navigate through the submenus.
Use the Help information for instructions to change options, save settings, and exit the utility.
Find the system date and time and set it.
Save your work and exit.