Archer wrote:

Got a new Lenovo G50-80 Laptop with Windows 10 pre-installed.

Tried to install Windows 7 Ultimate using a spare hard disk (put in
place of the original one). I had to set the BIOS to Legacy (instead
of UEFI).

The install went very well but none of the USB work. I tried USB
drivers but no improvement. I have also read so many sites in Google
on G50 lappie but could not get the solution.

Where did you look for the USB drivers to support that hardware under
that OS (Windows 7 - which you didn't mention its bitwidth)?

http://pcsupport.lenovo.com/us/en/pr...0-80/downloads

Did you install THEIR drivers after selecting the appropriate target OS?
Be sure you pick the correct bitwidth version. Bitwidth of drivers MUST
match the bitwidth of the OS.