Need Advice/example Autonumbering Column In A Table

I've been assigned to do the data access layer for an existing SQL database created by someone else. Amazingly enough, the primary table, the one containing all of the records that are central to the db and the whole project, has over 3000 entries and no unique identifer (autonumbered ID) column. The data in all of the other columns is repetitious so none of them can be used as a primary key. I have added a column called TaskAssignmentID, designated as an int data type. The goal is to somehow autofill this column with sequential numbers and then designate that column as the primary key. (don't you just love fixing other people's mistakes?) Any suggestions/examples on how to accomplish this the easiest, most efficient way?

For reference purposes, the table is called tbl_MCHS and the newly created column is called TaskAssignmentID. The data type of the column can be changed, if that would make it easier.

Tools available include Visual Studio 2005 (very familiar) and SQL Server 2005's SQL Server Management Studio (less familiar).


Things I am restricted from doing include blowing away the table and starting over or strangling the previous developer (I asked about both). :-)

Any and all suggestions, steps, or examples will be appreciated.

Thanks,

John