Want to know how to get there from here with Windows 7?  The following outlines supported and unsupported upgrade paths for multiple editions of the Windows 7 OS:

Unsupported Upgrade Scenarios

Upgrades to Windows 7 from the following operating systems are not supported:

• Windows 95, Windows 98, Windows Millennium Edition, Windows XP, Windows Vista® RTM, Windows Vista Starter, Windows 7 M3, Windows 7 Beta, Windows 7 RC, or Windows 7 IDS

• Windows NT® Server 4.0, Windows 2000 Server, Windows Server® 2003, Windows Server 2008, or Windows Server 2008 R2

• Pre-release in-place upgrades across milestones (for example, Windows 7 RC to Windows 7 RTM) are not supported.

Supported Upgrade Scenarios