While upgrading to SQL Server Express 2005 SP3, the error mentioned in the subject line is displayed and the upgrade fails.
I found a fix here that addresses this issue. It says:
quote:Copy the BPAClient.dll file located under C:\Program Files (x86)\Microsoft SQL Server\90\Setup Bootstrap\BPA\bin to C:\Program Files (x86)\Microsoft SQL Server\90\Setup Bootstrap\BPA. Run the SQL 2005 SP3 setup again.Works for 64 and 32 bit 2008 server.
If you have the 32-bit version of Server 2008, you'll use "Program Files" instead of "Program Files (x86)". The (x86) variant is used with 64-bit versions of Server 2008.