Ok I finally got hold of an unbranded OEM disc, as it turns out dpcdll.dll, pigen.dll and the 4 oembios files are exactly the same for Retail and OEM discs, there are however the following differences: acc_dis.ch_ accessib.ch_ eula.txt iesupp.ch_ iewebhlp.ch_ setupp.ini supp_ed.ch_ The help files on the OEM disc obviously tell the user to refer to the manufacturer instead of MS for support, it's not a major deal but if we are looking to install 100% faithful versions it might be useful.