To run the installer, click the link below.
Run the installer
If the installer script fails with Server Error, make sure that
ASP.NET version being used is 2.0 or above, not 1.1. You can find this
information in the last line of the error page, for instance:
You can change it to 2.0 in ASP.NET properties of the virtual folder.
You should also make sure the physical path to the virtual folder in
virtual directory properties does not contain trailing back-slash. The
virtual folder must be configured as an application as well.
If the above does not help, refer
WebMail Lite ASP.NET FAQ.