New Windows Vista?

I use a database on the new Microsoft XP on Windows Vista. I use the mail merge option on Microsoft Word to converge the two doents. The data in XP is names and addresses of people. Certain names won't show up on the merge file. I need them all to show up and I don't know how to fix this problem. I need all the names to show up all the time but I don't know how. I use the most updated version of the XP file and it still won't work. Any advice or help would be most appreciated!