This has been one of the most frustrating driver builds i've ever had to do. After adding the 760 to our driver standard, functionality became broken for the E6400 (it restarts as soon as WinPE loads). After struggling for a day to figure out what is going on, I learned something new!
One thing that I can't seem to find is some good documentation as to what command line options are available in WinPE 2.1 (Vista). A useful command that I learned in my travels is drvload:
1) Make sure you enable Command Line support in your boot image
2) Load all of your NIC driver candidates onto a USB Memory Stick
3) Boot your reference machine, when you get into WinPE, press F8 to bring up a command prompt
4) Use the following syntax: drvload inf [Path to INF]
Example: drvload e:\folder\driver.inf
5) Once it reports that the driver loaded successfully, run ipconfig to see if any IP info is listed (if you only get "Windows IP Configuration" then the driver is not correct, move onto the next one)
Once you find the driver that works in WinPE, import it into your Boot Image.