After you have burned the VistaPE ISO to a CD, make sure the computer is set to boot first from the CD/DVD drive, insert the VistaPE CD and reboot the computer.
On the Grub4DOS boot menu, select the VistaPE option.
Depending on your computer, it may take several minutes for VistaPE to load.
When the PE Shell Swapper program displays, click the Go button to finish loading VistaPE. (The default shell, LiteStep, is already selected.)
You should then be at a fully functional VistaPE desktop.
After a minute or so, you'll get a pop-up window when the wpeinit.exe program finishes. Just click the OK button to close it. If VistaPE was able to correctly detect and configure your NIC, network access should be available.