Those versions you are thinking about, which have both trial and a possibility of a full with a key, they come only with NEW PCs and are OEM versions. They can only be obtained with new pc or by corporate clients.
In case of your friend - install special trial version
, activate it with trial key (you will get it from that page). After 60 days it will deactivate itself, and you have to uninstall it. This version won't work after trial even with legal full key.
Once received legal full key you friend would have to delete trial version and reinstall retail (yes, I know that is not cool).
That is all because:
Retail version does not have trial mode and trial version from MS website can not be turned into a full one. And OEM versions are not available for legal download to general public.