I'm in the process of purchasing a Netbook for use while traveling. The included OS is XP, however, I would like to upgrade(?) to Windows 7.

My question: Does a Windows Upgrade have the same physical footprint and performance as a full install? Does an upgrade leave behind non used files/resources that were originally included in XP? If so, are there ways to reduce this?

I'm trying to reduce as much OS bloat as possible.

Please let me know if my question is unclear. Thanks.

Related to http://superuser.com/questions/60646/is-a-clean-install-really-better-than-an-upgrade however, this doesn't address the "leftovers" question.