Microsoft's anticipated $14.99 Windows 8 upgrade offer for people who buy Windows 7 PCs will go live tomorrow and last through January 31, 2013.

PCs preinstalled with Windows 7 Home Basic, Home Premium, Professional, or Ultimate can be cheaply upgraded to Windows 8 Pro under the offer. To qualify, Windows 7 PCs must be purchased between June 2, 2012, and Jan. 31, 2013, and have a valid Windows 7 OEM Certificate of Authenticity and product key.

To order the cheap upgrade, buyers will have to register through the Microsoft site by February 28, 2013 (but all purchases must be made by Jan. 31, as noted earlier). $14.99 is a great deal compared to Windows 7 upgrades, which start at $119.99.

The Release Preview of Windows 8 came out yesterday and can thus be expected to hit retail by October, or perhaps earlier.