I experienced an issue with SQL Server 2008 installation. The installation was not successful and the reason prompted was "SQL Express tools". And I have not installed any express tool :).

I searched the Internet and found out that the reason is "SQL Prompt" tool. Once uninstalled, the 2008 installation was successful.

Read this discussion for more info: http://forums.microsoft.com/TechNet/ShowPost.aspx?PostID=3457603&SiteID=17