For Outlook read this.
I doubt that the Windows 7 machine has OE as it doesn't normally run on W7. Do you mean Live Mail?
Excel and Word files are simply copied across. If they areboth networked then on the 7 machine you should be bale to see at least the public folders of the XP machine.
Bit puzzled why you want to copy. Is it more likely that you want to sync the files?