If you want to buy a PC with Windows 7 Home Basic, Home Premium, or Ultimate preinstalled, you'd better buy it today. As noted earlier this year, October 31 is Microsoft's cut-off date for OEM preinstalls of the consumer editions of Windows 7.

In truth, most major OEMs had all but ceased selling systems with these operating systems long ago. With Windows 8.1 available to OEMs at no cost in the form of its "with Bing" edition, Windows 7 becomes an expensive option.

Windows 7 Professional is still available as a preinstall for at least another year. There's no end date actually specified yet, but Microsoft says that it will give at least one year of notice before sales cease.