Microsoft has released a tool called the Windows 7 Upgrade Advisor Beta that can be installed and run on any PC that is running Windows7 RC, WindowsXP with Service Pack 2 or Windows Vista.

The tool is a little over 3MB and installs easily.  Please use the link below to snag the installer:

Windows 7 Upgrade Advisor Beta

Please keep in mind that the software is in Beta, so take all results with a grain of salt when running.