Per Microsoft -
[upgrade from] Windows XP (or any other operating system)
We recommend that you experience Windows 7 on a new PC.
For most, I did not like XP --> Vista upgrades; I don't like XP --> Windows 7 upgrades. Of course there are exceptions.
However, unlike with Vista, Microsoft itself is advising against XP --> Windows 7 upgrades (my interpretation).
Regards. . .