See this tutorial for more help:
Windows 8 clean install from iso using the machines own Windows 8 OEM licence
http://forum.notebookreview.com/sony-owners-lounge-forum/669429-official-2012-sony-s-series-owners-thread-594.html#post9078469
The BIOS does store the OEM key. If you make a clean install on an unparticioned HDD with an MSDN installer, it can detect the key. However, the windows edition of the key must match the edition of the installer (Pro, with or without Media Center Pack, Enterprise, etc.). If the two don't match, the installer will prompt to enter the key and activate Windows.
Here's another interesting tutorial, to install a different version of Windows 8:
Installing Windows 8 Pro over Standard OEM in your new Win8 Certified notebook
http://forum.notebookreview.com/asus/698920-installing-windows-8-pro-over-standard-oem-your-new-win8-certified-notebook.html