How to Restart Windows Without Restarting the Computer
This article describes how to restart Windows without restarting your computer.
To restart Windows without restarting your computer, follow these steps:
Click Start, and then click Shut Down.
Press and hold down the SHIFT key while you click Restart The Computer, and then click Yes.
As soon as the screen clears, release the SHIFT key.
NOTE: If you hold the SHIFT key too long, Windows restarts in Safe mode.
Read the full article: http://support.microsoft.com/kb/143272