Microsoft is considering offering Windows 7 on a USB stick to help users without CD or DVD drives upgrade their machines.
Microsoft has already made Windows 7 10% cheaper than Windows Vista.
Users get a free upgrade if they buy a Vista PC. When Windows 7 ships on 22 October 2009, Microsoft said eligible customers will be able to get a free upgrade to the equivalent Home, Premium, Business or Ultimate edition of Windows 7.
Windows 7 represents an important milestone for Microsoft, particularly for corporate users, who were dismayed that Windows Vista was not compatible with Windows XP. In Windows 7, Microsoft said it has addressed this limitation with an XP compatibility mode, which allows XP applications to run in a virtual machine.