Creating more optimize SQL Query

Hello, I am trying to update 1.5 million records on my mssql database table problem is the query keeps on executing forever i left it running for 12 hours and it still keeps on running and i dont think thats normal Now an expert can maybe make new optimized sql script for my database because this script im using is very old and im not good in scripting My Database: MSSQL 2005 My OS: Windows Server 2003 Thanks