He asked if he could clean install using an upgrade disk, not upgrade. Yes he can do a clean install using an upgrade disk.
There are step-by-step instructions here: http://www.winsupersite.com/win7/clean_install_upgrade_media.asp
Just a snippit to get the OP started:
Before we get started, here are some general guidelines to help you understand what will and won't work during Setup with Upgrade media. These tips and tricks represent the bulk of the information we didn't have before Microsoft shipped Windows 7 to millions of people in October 2009. Each of these was confirmed by the team at Microsoft that created the Windows 7 Setup technology.
If you have a previous version of Windows (XP or Vista), try launching Windows 7 Setup from that OS first, even if you want to wipe out the previous Windows verison. If you run Windows 7 Setup from your previous OS, Windows 7 will always activate.
or you can google it:http://www.google.com/search?aq=0&oq=use+windows+7+upgrade+disk&sourceid=chrome&ie=UTF-8&q=use+windows+7+upgrade+disk+for+full+install