This may be a limitation of WinPE, as the device you are trying to install is a network adapter that runs from the USB port. WinPE does not support Wireless networking either, as you need the full blown operating system to handle the interface with a wireless port, and I suspect the same is true of a USB device that is not block storage.
I would recommend checking with Linksys whether their drivers are actually compatible with WinPE, but I suspect the answer will be no.