In order to run without problems, Mobysaurus Thesaurus requires .NET Framework 2.0. To fix the issue, I suggest you reinstall only the Microsoft utility. Go to Start > Control Panel > Add or Remove Programs, select the program and then click Remove. After that, download the software from Microsoft Download Center and install it following the self-explained steps. If it doesn't work, use Google to obtain a download link for the Mobysaurus Thesaurus, save the file to your computer, launch the installer and follow the provided instructions.