This is extremely important - and nobody seems to have asked as far as I can tell.
For news on this see below - it is opaque :
Working to Fulfill our Legal Obligations in Europe for Windows 7 - Microsoft On The Issues
Windows 7 will be offered in Europe in all of the versions that will be available here in the United States, both 32- and 64-bit, with an “E” at the end of the product name (for instance, Windows 7 Home Premium E). The E versions of Windows 7 will ship at the same time as Windows 7 ships in the rest of the world, and they will be available in 23 European languages.
Does that mean the key will be an E version and will only work with E media?
Vital if you want get hold of alternate install media - e.g. to clean install using the key on the side of your OEM pre installed machine.
Or, as the original install media will quickly be redunded by the issue of a service pack - do you need the SP1 integrated .iso in the special E version ?
Could be a nightmare.