Thank you so much for your quick reply Coolname007! (The stupid newbie I am!) Can you please tell me where to find those 3 files, and then exactly where to copy them to? (To which folder, file?)
Thanks so much for your patience!
You will need to copy over your 3 XP boot files from C:/ (or whatever drive letter your XP drive is), instead of from C:/Program Files for example.

Copy them over to whatever drive your "system" drive is...and put them in the "root" as well. That is simply what the "root" of a partition means.
GL and if you have any more questions, then don't hesitate to ask !
-Coolname007
EDIT: And you will need to unhide the system files first by going to Control Panel>View>Folder Options>and unselecting "Hide system files" and selecting "Show Hidden Files and Folders".
Addendum:
Vista will write boot-code and if he doesn't changed his boot device and the installer picks up as it should he won't have that problem.
He is using Win 7, not Vista, though, Justin...
And I still think he will need to have the XP boot files on the "system" root before the entry created in the Win 7 bootloader for XP will work...
-Coolname007