MS licensing sold for for home editions will all be single usage. MS does offer volume licensing for business and institution (educational) use. You don't find those through normal channels. Some software these days is allowing a person to install a copy on both a desktop and a mobile device. This does not go for operating systems. It's meant for the person who needs to work at home and away from home. The intention of such licenses is that there will never be use of both copies of the software at the same time. I like this idea. MS also offers....or has offered....multiple uses of some software. I believe that their Office products for home and student use may allow up to 3 installations. This is a good deal, IMO. I expect there are good business reasons for this. But, as always, read the EULA yourself. It's not always clear. I presume your pre-order is for an upgrade copy. This will surely be for a single PC.
If I have pre-ordered a copy of Windows 7 Home Premium to install on my PCs running Vista Home Premium, how many uses of the Product Key am I allowed per copy of the upgrade? Is it only a single use for a single computer? I know this may be a stupid question, but I am very confused by the licensing agreements.