If you have experience editing critical files, you can edit and save the boot.ini file with wordpad. The boot.ini file is in the root of C:\CAUTION:
If you have not done this before, be very careful. If you delete wrong Windows boot option, you may not be able to boot to either operating system.OR
you can download and install EasyBCD
(it's free), and it will provide guidance on how to edit the file to boot directly to Win XP Home. After you have done that, restart, and after successful boot to Win XP Home, you can open windows explorer and delete the XP Pro Windows folder fro the C: drive. CAUTION:
Again be sure which windows folder you are deleting before you do so.