VistaBootPRO will not help to manage XP/2k/2k3 multi-boot environments -- but only environments including Vista and/or Server 2008 (and Windows 7).
so you should forget VistaBootPRO (although you should first uninstall the Vista bootloader if you have installed it), and then use boot.ini to create a proper XP/XP dual-boot environment.
When you open boot.ini (in notepad) you should see a single line representing your single working boot option.
Copy that line right below, and then change the hard drive number in the second line -- probably from (0) to (1), and if desired customize the OS description text.
Then reboot, and your dual boot option should be working.
Note that if you have cloned the XP from another computer that some settings may not work in this new location, and at the very least a "repair install" of XP would be recommended -- I personally would do a clean install once I was sure data and stuff was safe in this second drive.