You want to look for Outlook.pst on your old XP drive
I don't remember exactly where it was located in XP, something like:
c;\Documents and Settings\Your name\AppData\Local\Microsoft\Outlook

and copy it to your Vista C Drive in the following location

C:\Users\Your Name\AppData\Local\Microsoft\Outlook\

something like that

the Outlook.pst file is where all your Outlook info is located in