here are a couple of reads on it:
http://superuser.com/questions/42263/how-to-install-windows-7-from-the-network
Source machine:
This machine must have a static IPv4 address. This example will use 192.168.0.1.
This machine must have a Windows installation in a shared folder somewhere. This example will use .\win7
This example will log in to the source machine with user TEST and password test.
Use tftpboot to fire up a DCHP server (gives an IP to a computer when requested).
This will also start a TFTP server for all of the file transfers.
There should be a folder called boot\ in the tftpboot directory which contains an installation of Windows PE.
Start tftp64.exe (or tftp32.exe), open the settings, use default settings, and change:
•IP pool starting addresss: Whatever, the pool of IPs to draw from
•Size of pool: Must be > 2
•Boot File: boot\pxeboot.com (will dump into Windows PE environment)
•Mask: 255.255.255.0 works fine.
•Uncheck "Ping address before assignation"
•Check "Bind DHCP to this address"
Restart the program to ensure changes are in effect.
Receiver machine:
Run a network boot from the receiver machine. (The DHCP server will assign an IP).
The boot file will be transferred and run. Press F12 to tell WindowsPE to do something.
Wait a while (30-60 seconds). A command prompt will appear and load. Wait until a cursor is available.
A drive must be assigned to the root folder on the Source machine. To do this:
X:\Windows\system32>net use z: \\192.168.0.1\win7
A username of a user on the source machine, and password, must be entered.
Enter the user name for '192.168.0.1': 192.168.0.1\TEST
Enter the password for 192.169.0.1: test
The command completed successfully.
Navigate over to the new directory (z:\) and fire away. Commands will have a long delay but should work eventually.
http://technet.microsoft.com/en-us/magazine/2008.07.desktopfiles.aspx
Really don't have much experience at this.