It would have been easier if you had exported the HUDs from the old HM2 installation but you can still recover them manually.
C:\Users\{UserName}\AppData\Roaming\HoldemManager\ Config\prefs.xml is the file you need to copy from the old installation to the new install. If you can't see it, turn off the windows option that is hiding that directory -
http://faq.holdemmanager.com/questio...es+in+Windows+
You may also want to copy/paste the original hand history files as well, if you might ever want to import them to your database on the computer. All original hands that are auto-imported get moved to an archive for performance reasons. Your \HM2Archive is in C:\HM2Archive by default, but you may have put it anywhere. The archive should be organized by \Month\DayOfMonth (example: D:\HM2Archive\2009\07\31) or if it was auto-imported with 7283+ it would be in \HM2Archive\SiteName\YYYY\MM\DD.* It is configured in the Site Setup - Auto Import Folders menu.