From your description, you did not perform an "overinstall", if you have two separate OS'es installed.
You may not be able to do what you are trying to do... If WinXP (home) is installed on the first partition (which would seem to be the case from your post), with WinXP Pro installed on the second partition (for simplicity purposes, I'll call partition 1 "C:", and partition 2 :D:"), and your data and programs are on C:, you can remove the system files from C: (only), and adjust your boot.ini file to reflect only one OS, but the programs installed on C: will no longer work (your data will remain).
If you simply alter your boot.ini to only reflect the existence of WinXP Pro (drive D:), leaving the other system intact, you may not be able to launch the programs either, as they will be associated to the original (Home) installation.
Your best best would be to delete the unwanted system (leaving your data) and re-install all of your programs to WinXP.
There may be other solutions, perhaps third party tools, but the scenario you initially describe does not lend itself to an easy solution
I agree, but if the first partition was an upgrade from Win 98 you could uninstall the XP by these stepps from Microsoft.
How to remove Windows XP
To remove Windows XP, follow these steps:1. Restart your computer in Safe mode. To do this, press the F8 key while Windows is starting.
2. Log on with an account that has administrative credentials.
3. Click Start, click Control Panel, and then double-click Add or Remove Programs.
4. In the list of installed programs, double-click Uninstall Windows XP.
Note If Uninstall Windows XP is not in the list of installed programs, you must manually reinstall Windows 98 or Windows Millennium Edition. In this case, make sure that you back up all your critical data before you reinstall Windows 98 or Windows Millennium Edition.
5. When you receive the following message, click Yes to start the Windows XP removal:
Are you sure you want to uninstall Windows XP and restore your previous operating system?
6. After Windows XP is removed, your computer restarts to the previously-installed operating system.
However you might try partition majic. This program will let you remane the partitions and designate boot sequences. It will do alot more to. I used it befor to install a slave drive and formated it for then moved files from one drive to the next. Made the slave drive a then reinstalled the NT o/s on the c drive.
Something similar might help you.