Can't help you with getting a legal key, but having recently had to install Windows 7 Ultimate and OS-X Lion as dual-boot option on a company's collection of shiny new MacBooks I remain in awe of Microsoft's business practices.
Installing the Mac OS: there ya go buddy, see what you need, take what you want, download it, stick on a USB drive, update it, whatever suits, that's a couple of quid tops or maybe not and best of luck to you, have fun.
Installing Windows: Over 300 euro a pop, this version won't run on that machine, this version isn't in stock but we can order it from the warehouse but that'll have to ship from England so it'll take a few days (An overseas warehouse. For software. In 2012), no you can only use each licence once, no that version is OEM and only for a specific new factory-built machine, no you must register NOW, you MUST sign-up, no tech-support or updates until you DO, oh and please DROKK OFF.
Contrasting experiences to say the least. As the dim-but-happy user of pretty-much only open-source software for the past year I really wonder how this sort of 20th C protectionist thing is still viable.