Just want to cheer som info.. Went to shop an bought a brand new acer aspire E1, included preinstall of W8. I desided to make a clean install, took my orginal W8 pro 64 bit dvd (downloaded from MSDN), formated te disk and started to install new CLEAN windows. I am owner of a MAK key with many activations so i was planing to use this key on my new install. But, under install, i was never asked to type any key.. And after install was complete, the OS was OEM activated.. And, it wasnt W8 pro, like the install dvd i put in the dvd rom. It was the core version that followed the pc from the store. But it was a clean install offcourse. It seems no need to type any key, on clean installs on computers delivered with W8 OEM-SLP licenses.
For the new OEM scheme for Microsoft OS's, the Product Key is located in the Computers BIOS. To avoid the automatic use of the OEM Key you'll need to edit the Installation Media and place an EFI file there which lets you chose the version of Windows 8 to be installed. Or, you need to download and plain BIOS from Acer (if available) and change the Computer's BIOS to that one. That should do the work. Hope that helps.