pretty new to Qlikview myself, but I'm pretty sure you can just drop the 'join' part alltogether. QlikView is going to concatenate all of your password files together (because they have the same number of fields, and each field has the same name), and then join them by name to your user table (assuming the field names are the same). You shouldn't need to explicitly join anything.
The Access table has a different structure than the password spreadsheets, so any concatenation would have be explicit, using the CONCATENATE load statement prefix.
We need joins here, anyway. Concatenation would add rows to this table, but we want the same number of rows as the original Access table inline load, only with the addition of a field containing password values.
You don't want to be executing two separate joins here, and the use of outer joins, specifically, is how you are ending up with multiple rows per user. You may want to read about what outer joins are, but your first one is adding the password column to the Access table, and the second one is doing something else.
Concatenate load all of your spreadsheets into one temp table, then left join that temp table to your Access table. You can then drop the temp table.