Hi bookie56,
Most Windows 7 drivers are already available in Win7PE_SE

.
you can of course added some specific drivers (eg: LAN, WLAN) in your Win7Pe and also integrated driversPacks (eg: chipsets, mass storage) with the Driver Integration script.
But as you said, careful not to inject too many drivers for keeping an acceptable wim file size, for the starting time and the size occupied in RAM.
You can also use the script "Driver Package Installer" which uses DPInst to add drivers to your running PE
This one allows to copy or unpack drivers packages onto your media to the outside of the wim file (Not in Ram).
and load them, if needed, in your running PE.
These 2 scripts allows you to control which ones you want integrated into the WIM and which are available after booting the PE.
This is a personal choice depending on which machine you want to run your PE and your Win7PE use.
Remembering that most Win7 drivers are already included.
Regarding your error, difficult to help you without log.
You can run "Driver Integration" by selecting the "Pause (win7)" checkBox with the "Show process".
With this, you will have a break at the end of the integration for better see what happens.
Regards,
