This particular problem took a while to find all the information for the fix, so I figured I should post a summary for other folks.
While installing one of our standard SQL 2005 developer tools packages, one of the desktop staff received a 1603 failure. This was fairly unusual, as this particular installation has been performed multiple times without fail. Needless to say, I began digging into the machine to find the issue.
The first place I checked was the SQL summary log:
Machine : SYDJGYX22SINCS
Product : MSXML 6 Service Pack 2 (KB973686)
Product Version : 6.20.2003.0
Install : Failed
Log File : C:\Program Files\Microsoft SQL Server\90\Setup Bootstrap\LOG\Files\SQLSetup0005_SYDJGYX22SINCS_MSXML6_1.log
Error Number : 1603
Seeing this, I pulled up the Windows Application Event log and found:
I had, in the past, encountered an issue where if MSXML SP2 was already installed on a machine and an attempt was made to install it again (via a package), it would fail. So I removed the SP and received another failure:
Nothing I tried allowed me to remove the SP. I continued to receive msi corruption messages. I found a few posts about this particular problem and a recommendation for using the Windows Installer Clean Up Utility was given. I obtained the tool from here -
http://support.microsoft.com/kb/290301. It worked like a charm - removed the problem application (from the Control Panel as well) and allowed the package to install properly.
Hope this helps others.