Is it worth buying a Windows 7 upgrade package or should I buy a OEM copy?

"There is no difference between the versions, except in the terms of use, i.e. when/where you can install it.

It is legal for you to buy an OEM copy of Windows, but they are effectively ""one-shot"" installs, they live and die on the hardware they are installed on, I'm not sure if that means you can reactivate if HDD fails and you replace it even though your system is effectively the same... Some suppliers will only supply an OEM copy with some kind of hardware such as a drive, but YMMV.

Getting the full version means that you can move your copy of Windows to a new machine and re-activate it without worrying, the worst you'll have to do is phone Microsoft and tell them that the old copy of Windows is gone. I would assume that so long as you keep the media for Windows Vista then the upgrade version should be the same."

"No you can not upgrade from different languages. The OEM version does come with a upgrade option as well as a full install. Since you have a german copy you NEED a German Windows 7.

I upgraded a friends computer to windows 7 from vista home pre but he had a spanish version; I could NOT upgrade. Windows said the reason was the language. I had to upgrade with a spanish version then installed the english language pack so he could keep all of his programs AND have an english looking version of windows 7."