Yes you will be able to do a clean install, a lot of people seem to think that 'Upgrade' editions mean you can’t do a clean install, well to date, with MS upgrade edition OS's you have always been able to, however, you do need a valid full OS install disk from the list that is appropriate for upgrade. So, if you have a retail XP Home (full version) disk, you can upgrade to W7 Home Edition, and the same is true for Pro.
All you do (or have done in the past) is start the installation by booting from the cd/dvd as you would normally, and eventually it'll ask you for the older OS disk with a full version on it, just put that in the disk drive, it'll either accept or decline it and then put the disk you are actually installing from back in and it'll let you do a clean install …unless it declined it, but I’ve only seen that happen when trying to upgrade from an incorrect version of Windows.
Simple as that.