Windows 7 can be installed without user intervention by placing a specially formatted XML file on a USB drive or floppy disk before booting from the installation DVD. The file's name is either Autounattend.xml (my preference) or Unattend.xml. The file is placed in the root directory of a USB drive or floppy disk.

The best way to create Autounattend.xml is to install Windows Automated Installation Kit (AIK). Then you have to copy install.wim file from the Windows 7 installation media, open install.wim in Windows System Image Manager, and create a catalog for it (takes a long time) before you can create the first Autounattend.xml. To spare all these steps, I provide a sample Autounattend.xml that has worked for me many times.