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You can use the upgrade to go from Home to Pro. You can also do a clean install of Pro without loading Home first. You will have to have the Home disk handy however because Pro will ask for a previous version of Windows to do the upgrade. Pro will ask you to place the Home CD in the CDR and it will check to make sure it is a valid version. Once it sees that it is then the install will begin.

If buy chance your XP Home is a OEM version (HP,DELL, etc.) with recovery disk and not the Full version of XP Home this will not work and you will have to have XP Home loaded on the system before it will upgrade..........

I hope this helps.........