Information that Tech ARP has gathered about the Windows 7 Upgrade Program seems to be inline with a previous rumor about three upgrade scenarios
for Vista to Windows 7: Home Premium to Home Premium, Business to Professional, and Ultimate to Ultimate. While Microsoft has not revealed any final dates for the upgrade program yet, rumor has it that the program eligibility will begin on July 1, 2009.
In other words, if you purchase a computer with Vista preloaded on it, on or after July 1, up to some undecided date (OEMs can choose to have an even shorter timeframe within the one Microsoft will give), you will have the option to upgrade to Windows 7 for free when it becomes available.
Full Story: Buy a Vista PC as of July 1, upgrade to Windows 7 for free