Thanks to Microsoft's sluggishness in getting their Vista operating system out, and thus, missing Christmas '06, they're offering free upgrade coupons to new computer buyers starting October. If you buy a "Vista-capable PC" later this year, you'll get a coupon for a free upgrade to Windows Vista when it does come out Q1 2007.
This promotion is most likely a way to placate angry PC manufacturers like Dell, who would see a sharp drop in sales thanks to people waiting until Vista was out to buy a new PC. Instead, now they can still go ahead an buy a computer for Christmas and still get their Vista-fix next year. It's a win-win for manufacturers and customers.
Free Windows Vista Upgrade Coupons for Windows XP Users [Digital Inspiration via Get a free upgrade to Windows Vista]