At my company, we're migrating from Windows XP to Windows 7. We've got 2 home made applications written in C# with the .NET framework 3.5. They use ClickOnce to be installed. We're in the test phase and the installation of these soft crashes on some Windows 7 machines and doesn't on others. The difference between these machines should be the configuration of the policies. The only error message we've got is this one: I tried to find some logs somewhere but there's nothing neither in the Event Viewer nor in the applications log (wich are poorly logged, then I'm not expecting miracle from this side :( ) These applications: work with FTP servers use WCF use old deprecated libraries (as I'm not at work, I'll edit this post when I'll have the info) use nHibernate 2 use LLBLGen use a deprecated Infragistics library export data into Excel files Did you encounter such an issue while migrating? Or do you have an idea where I should investigate on?