Cannot install Windows 8 Pro in place of Windows 8 (vaio)

Hi people,

I've just buy a new laptop Sony Vaio S15

how come with a preinstalled Windows 8 (+ all crapware )

So I had in stock a SSD and which to install inside this laptop and install a new windows 8 pro in the same time.

But this seem to bug ! i've a USB key ready with the Windows 8 pro installation stuff.

and when I install this He don't ask me for any serial number !! and install by default windows 8 "home" !! so how install Windows 8 Pro ?

thx people