You will get Error code 0x84B40000 when installing SQL Server 2008 Express. It will say:
"SQL Server Setup has encountered the following error: Attributes do not match. Present attributes (Directory, Compressed) , included attributes (0), excluded attributes (Compressed, Encrypted). Error code 0x84B40000."
To Resolve: Edit
1. Open "My Computer" and right click on the OS Drive's Properties. If the checkbox is checked under "compress this drive to save disk space", uncheck it. SQL will not install on drives that are compressed.