Change Windows XP Home to Windows XP Professional

The functionalities of Windows XP pro are hidden in the home CD. This is the walkthrough to use them.

Steps

Enable the features found in Windows XP Professional on your Windows XP Home Edition installation with this hack. It will allow you to turn your Windows XP Home CD into a Windows XP Professional CD.
Copy the root directory and the i386 directory of the Windows XP CD to your hard drive.
Extract the Boot sector of your Windows XP CD.
Click START-->RUN-->REGEDIT
Highlight HKEY_LOCAL_MACHINE
Click FILE-->LOAD HIVE and select the Setupreg.hiv file. This file is located on your Windows XP CD in the i386 folder. Regedit will prompt for a name to attach the hive to, "HOMEKEY" is the assumed value used in these steps (click OK to complete the Load Hive process.
Locate the following registry key:HKEY_LOCAL_MACHINE\Homekey\ControlSet001\Services\setupdd
Edit the DEFAULT key and change the following values to 00.
01 to 00 and 02 to 00
Change the name to the value HOMEKEY to anything.
Highlight HOMEKEY and select FILE-->UNLOAD HIVE
You can now burn the data on your hard drive to a CD. Then use the CD to install Windows XP. Be sure to make the CD bootable. You can use the instructions here to help you do that.

If your Registry Editor fails to load the hive, try removing the read-only property from SETUPREG.HIV
Although in most cases you will be able to use advanced network options, such as domains, it has been reported that many people couldn't use them. If it does happen, try repeating the steps and burning a new CD.
If your Windows XP CD does not contain Service Pack 2, you might want to Slipstream Your Windows XP CD first as you will not be able to upgrade an installation after using the CD.

Even working exactly as XP PRO, it is still XP home. So, if you need to use a program that requires XP Pro, this hack is not suitable for you.