A PC running Windows XP Professional SP3 received the following when attempting to install SQL Server 2005 Express: “SQL Server Setup Unexpectedly Failed. For more information, review the Setup summary log file.” The Setup summary log (…Program Files\Microsoft SQL Server\90\Setup Bootstrap\Log) mentions an error: Action “ParseBootstrapOptionsAction” failed during execution.
After some searching, I came across a post which I cannot find now. It said to ensure the following REG_EXPAND_SZ was added in the Windows Registry:
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\User Shell Folders\AppData
For this particular PC, I had to change the value to %USERPROFILE%\local\AppData\ to get it to work.