Microsoft launched SQL Server 2005 in November, 2005. This build was called the RTM version.
In April, 2006, we launched Service Pack 1 which included a lot of new features and fixes for known bugs. Check out my blog here to learn more about SP1.
However, Microsoft had to freeze any code changes into the SP1 tree at build 9.0.1530. As a result, any hotfix that you received from Microsoft SQL Server support team that had a build higher than this (and less than 2153) is not included in SP1.
In May, 2006, Microsoft launched the cumulative package for SQL 2005, which included all these hotfixes which couldn't make it to SQL 2005 SP1.
Download 2153 cumulative package
You can download the cumulative packages from http://support.microsoft.com/kb/918222