Microsoft Windows 7 is the successor to Vista but for most people will be their first upgrade from XP.
Performing a clean install from an upgrade disk
As noted on http://the.taoofmac.com/space/com/Microsoft/Windows/7 the following steps will allow you to perform a clean installation from a upgrade disk. After performing a clean installation with the upgrade disc do the following:
- regedit.exe your way to HKEY_LOCAL_MACHINE/Software/Microsoft/Windows/CurrentVersion/Setup/OOBE/
- change MediaBootInstall from 1 to 0
- In a command prompt (run under admin using Ctrl Shift Enter) slmgr /rearm
- Reboot and activate