First, I have to say that you really need a good reason to do this.
For home use, I recommend either Windows XP Home or XP Professional, your choice, but I also recommend that you pick one and stay with it — all your home machines should be running XP Home or they should be running XP Pro. Home is a little more cutesy and has more functions hidden, and it is missing some of the more sophisticated networking functions.
Having said that, I recently upgraded an XP Home installation to XP Professional. The upgrade process was smooth as silk.
In this particular case, the computer was going to be used by a child for remote access to her school’s network. The school had a Windows “domain controller” for access control to the network, which forced the use of Windows XP Pro. That is one of the few reasons to purchase XP Pro for non-business use.
First, as with any major change, I backed up your machine. In this case, I hooked the machine up to my network and used Karen Kenworthy’s Replicator (www.karenware.com) to copy everything to some available hard drive space. Replicator will gracefully skip files that are uncopyable, such as the windows registry, by file copy methods. Windows Explorer, on the other hand, simply stops at the first hint of a problem.
I did an anti-virus scan and an anti-spyware scans with Microsoft AntiSpyware (beta) and Spybot Search & Destroy, and then rebooted the computer.
My first thought was to boot the Windows XP Pro Upgrade CD. Wrong. There was not an upgrade option this route. I needed to boot the installed Windows XP Home and then insert the Windows XP Pro Upgrade CD.
After inserting the XP Upgrade CD, it will autorun. One of the options is “Install.” When I selected this option, I saw one of the smoothest Windows installations I have ever seen. I had to put in the XP Pro product key, and, of course, I had to set up the time zone and such. But, it was smooth, smooth and trouble-free.
[originally published in 2006 ]

Terry; Hi, Great articule! I would like to do an upgrade also, but one thing you didn’t clarify was that is the disc used is a regular XP disc or is there another one needed wich would be upgrade only, such as MS’s done with Win7, or is the upgrade function already on the regular disc? Thanks -E-
It has to be an upgrade CD. The retail CD and the OEM CD’s are set up only to do a fresh install.
What if you already have XP Service Pack 3 installed? Is it then impossible to upgrades to XP Professional? Thank you. Irvin Watkins
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