Win7PE can't connect to the internet

Hi,

I used WinBuilder to install the Windows 7 PE on my external hard drive.
The installation went very smooth and I got no errors.

I am able to boot my external hard drive without any problems,
but when the desktop appears, a message pops up:

"ERROR
No network cards detected!
Program will be Exit now."   (<-- no, I didn't make a mistake, it really says that )

Also, when I open Opera, it says "Network problem".
I tried installing several driver packs, but that didn't help.

I'd be very happy if some one could help me
(sorry if I'm giving you wrong/irrelevant info, this is the first time I try something like this.)

Thanks!!