Why not over complicate this? The original chart contained 66 cells but was later pared down to 14 by blogger Ed Bott. The key sticking point is the ability to "upgrade" install Windows 7 over Vista and XP rather than forcing users to do a "clean install".

In my opinion Windows users are better off conducting a clean install when upgrading their OS, especially if the prior OS is exhibiting slowness, quirkiness or isn’t running just right. I keep my systems incredibly clean but still find myself reinstalling every 2-3 years due to hardware replacement or upgrades. Regardless it’s probably a better idea to back up your data, lay hands on the original CD/DVD application media and start fresh with Windows 7.