Its basically a short and simple registry hack
The hack will not install and add in all the features from Windows XP Professional that Windows XP Home lacks of, such as Remote Desktop Server and Group Policy Editor (GPedit) utility tools, which have been removed on Windows XP Home edition. Some functions which turned off and disabled via integrated switches which read from registry flag whether it’s Home or Professional edition, such as EFS, RAID support and ability to join domain, may or may not work after migration. Basically, the trick only work to let Windows XP recognizes itself as Professional edition...
Its not recommended as the OS you are using is still XP home and may surely cause problems and compatibility issues when installing updates from microsoft...