You can check this solution
Please do let us know if this works.
I am pasting the comment in which solution is given on this link for more help.
OK now is the truth. This is the solution.
I assume all of you is using USB drive to install.
When Windows is asking for driver, just click Cancel. You will be brought back to the welcome screen. At the welcome screen, remove your
USB drive, insert it back to DIFFERENT USB PORT. Click Install Now
again. The installation process will be like usual.
This problem happened to all new version of updated Windows 7 installer. I think, it is due to failure of Windows installer to
remain its detection to the USB drive. It lost the connection, and
became confused, don't know where to find the USB drive it used to
When we re-insert the USB drive, Windows installer will detect the USB drive back, and continue like usual.
Good luck and cheers! TQ.