Reformatted Laptop; need to upload Excel file into Outlook Addresses

I had to reformat my laptop. (XP) I backed up my add’l address book in an Excel format. Now when I try to upload it into Outlook’s Personal Address (add’l Address Book)- the message states that the file has to be in a *PAB extension. (Obviously that is not how I saved the file, and I can’t change the PAB to anything else in order to upload? Any HELP??