Hello Juan, and welcome to Vista Forums.
A clean install is formatting the hard drive to erase and delete everything on it. A factory recovery or restore from your recovery partition or recovery disks will format your hard drive and restore it back like the day you first got your computer instead.
If you have a retail upgrade version of Vista that you want to upgrade to, then you can use the method below to do a clean install with if that is what you are wanting to do. Clean Install From Upgrade Vista
Hope this helps,