Uninstall the application using its uninstaller or Add or Remove Programs feature:
If you use Windows XP or bellow you can go to Start > Control Panel > Add or Remove Programs. In the Currently installed programs box, click on the SharpReader program and then click Remove.
If you have Windows Vista or above you need to go to Start > Control Panel > Programs > Programs and Features. Select the SharpReader application and click on Uninstall.
After that, install .NET Framework 2.0, restart your computer and download and install the full version of the software from the official web page. This should fix your issues.