However, the company is emphasizing two main SKUs (stock-keeping units) of the forthcoming OS -- Windows 7 Home Premium and Windows 7 Professional -- saying these are the ones most customers will buy, according to on Microsoft's Web site.

With Windows 7, Microsoft hopes it will be easier for customers to decide which edition of the OS is right for them. By doing so, the company once again seems to be trying to learn from mistakes it made with the release of Windows Vista, premium versions of which had special hardware requirements that hindered customers' transition from XP and confused users as to which edition they should purchase.

When Microsoft released Vista, premium versions such as Windows Vista Ultimate and Windows Vista Home Premium did not run on many PCs that already were running Windows XP. Microsoft tried to give hardware partners and customers fair warning of this and through a controversial program had OEMs put stickers on new PCs to let customers know which version of Vista those machines could run.

Still, many customers did not feel Vista hardware requirements were communicated effectively and Microsoft is still over that sticker program, called "Windows Vista Capable."

In addition to Home Premium and Professional, Windows 7 will come in the following editions that mirror Vista's SKUs: Windows 7 Starter; Windows 7 Home Basic; Windows 7 Enterprise; and Windows 7 Ultimate.