If you have to change the type of a key column on SQL Server, and the new column type has to be integer, and even identity, you can do it by using some criteria in order to get the rows ordered (PK= index clustered= order by in physical disk by this column)..
We will change the type of the PK column of a table in a sample with 2 typical invoice tables master-detail where the key columns are nchar. 'invheader.invoiceid' is the primary key of the master table and 'invlines.lineid' is the primary key of the detail table..
With SQL Server, when we forget or we lose the password of the DBA user 'sa', and we are the administrators of the database, we have a little problem.
It's easy to forget this password because probably we have our own user administrator and don't use to log in with the sa account. We also could have inherited the administration of a SQL Server database, with any documentation about the sa account or we coul'd have installed a database and deleted the login with admin privileges without knowing the password of the sa user.
For all this situations there is a better solution than reinstalling the database..