Mohammad Daoud has a new post with SQL code to FIX SQL Orphaned Users (Create SQL Users exists in a restored database in SQL Users)
FIX SQL Orphaned Users (Create SQL Users exists in a restored database in SQL Users)
SQL & DataInstall, Upgrade & Admin
Archived post from 2010. Dynamics GP and the links it points to have changed since; check current documentation before relying on version-specific steps.