Acer

Acer lists three steps on its upgrade page.

1. Buy a qualifying PC running Windows Vista from June 26, 2009 through January 31, 2010.

2. Order your Windows 7 upgrade, which sends you to a third-party Web site to register.

3. Your upgrade will be mailed to you after Windows 7 becomes available.

Check out the full details here: http://www.acer.com/windows7upgrade/