The Sitefinity web installer installs Sitefinity in a default folder located in Program Files or a custom folder chosen by the user. Under that folder there are the Sitefinity.exe and two folders, the "_emptyProject" folder and the Projects folder. If you like to have another web site, you don't need to install Sitefinity again. You need to open the Sitefinity project manager from the Sitefinity.exe and click on the "Create new project" button. It will prompt you to set a location for your new project on your hard drive.
When you install Sitefinity, the installer sets up a default project in the Projects folder and configures it automatically. If you run the installer again, it will create a default project with different index (e.g. Default2) because we don't erase old projects. The _emptyProject folder is a system folder for Sitefinity and it is not advisable to edit its contents. You can amend the contents of each Project folder inside the "Projects" folder. If you have worked in the _emptyProject folder, and if you have installed Sitefinity again, the changes you have made in that folder are lost. If you have a Sitefinity database and if you would like to set the connection string of your project to point to the database, you need to go to the ..\App_Data\Sitefinity\Configuration\DataConfig.config file in your project folder and change the connection string in that file.
the Telerik team