as i recall, i think the default is your "my documents" folder. if you've already done the backup, search your pc for a .ipd file, that's the extension of the backup file. if you haven't yet done a backup you can choose your location when you go to backup.
also, in case you're not aware, you can backup JUST the pw keeper (instead of doing a backup of your entire BB) by doing advanced backup and choosing pw keeper, moving it over to the left column and hitting file>save (or save as if you want to choose your location and give it a diff name). however, it's always a good idea to periodically back up the entire BB.
