ERROR - The row value(s) updated or deleted either do not make the row unique or they alter multiple rows.

i am getting the above error on my database i have 2 rows with the same info on and another 2 with the same info on.  example:
ID    username   password
1            bob       bob
1            bob       bob
1           john       john
1           john        john
 
I know this is a fault with ms sql 2005 however how do i fix it?
Ive found this link which explains everything but how do i start a query.  I tried clicking on new query and copying the code.  What is table1 meant to be?  the database is dbl.tbl_admin.  It wont find my da ...