Welcome to the community. 
Sorry to see you have an issue.
Since you have Windows 7, it is likely that your .NET Framework is out of date. As Windows 7 support has been ended by Microsoft it no longer receives important updates, such as for .NET Framework.
The links to update this are here, under the last header in the post: I can’t Install WeMod / "There was a error installing the application" - #2 by Ravenfyre. You’d have found this post using the search button on the forum before posting.