Microsoft plans to market several versions of Vista but will distribute all of the OS bits with every product shipped so users can easily unlock and step up to more full-featured versions using electronic keys, sources said.

No matter which edition you buy you get all the bits and a key to unlock it. Everyone will have all the bits," said one source familiar with Microsoft's plans. "Right now we maintain master images for each version of Windows XP and it's a lot of work. Now there's just one master image.

Having a master Windows Vista operating system means customers that buy PCs preloaded with one Vista SKU, Home Basic, for example, will be able to punch their credit card into a Microsoft Web site to unlock Vista Home Premium and more speedily deploy media center features without an on-site visit or requiring a wipe and reload of the system.(via: WinInsider)