I'm going to upgrade from XP Home SP2 to Pro SP3. I upgraded from Home SP1 to SP2 and the results were not very good. Everything works fine but the bootup and shutdown times are much slower. The company I worked for went out of business and one of the things we all got out of the deal is a XP Pro SP3 disk and license. I am going to upgrade to it and was wondering if it would be best to do a complete reformat or just install it as an upgrade?