There are three logs you can look at. The HII client log (x:\windows\system32 in winpe), the dism log (x:\widnows\system32 in winpe), and the setupapi.offline.log (%WINDIR%\inf\setupapi.offline.log). They will show if there were errors installing a certain driver. For Windows 7 you would only need the NDIS62 drivers.
You could inject the driver directly into the image in the image file in the windows\inf directory and the os would automatically pick them up. Not really the preferred method because then you have to maintain and update the image file as that driver is updated or new ones are required. Better to troubleshoot the hii issue.