installation of SQL Server Management Studio 2008 Express stops at "Feature Selection"

I was unable to install SSMSE (SQL Server Management Studio 2008 Express). The installation stopped at the step “Features Selection”. There are two Shared Features for selection: Management Tools – Basic; and SQL Client Connectivity SDK. The check boxes should be blank. However both check boxes were checked and greyed. No matter how I select the option it showed error message “To continue one or more features must be selected”. I assume that somehow the management had been installed in my computer before. I might have to remove some program before install SSMSE. I installed MS SQL Server 2008 Express in 2010. In my notebook. The path for the icon MS SQL Server 2008 Express is actually ssms.exe (not sqlservr.exe), that is located in C:\Program Files\Microsoft SQL Server\100\Tools\Binn\VSShell\Common7\IDE. The size and date is 1,298,456 2008/0 ...