vb.net 2010 web form app using .net framework

Question

I just started to be assigned a work station that was low on memory so I accidently removed the wrong version of the .net framework. To correct the problem, I downloaded .net framework 4.0 since that is what the application uses. This web form application uses vb.net 2010 visual studio ide.

I problem is I probably downloaded the wrong version. The application probably was using a version number 4.3 I am guessing.

Thus I am trying to determine what I need to do to solve the problem.

Here is where the steps of where the problem lies:

1. When I try to debug the application, I get the following error message:

Once I see the above message, I just click the OK button. I do not know where to point the application.

2. After that point I get lots of messages that look like the following:

AttendanceLetters\App_Code\mylistbox.vb(1): Build (web): Reference assemblies for target .NET Framework version not found; please ensure they are installed, or select a valid target version.

Thus to solve the problem can you tell me the following:

1. Can you tell me and/or point to a url (link) that will solve the problem tell me how and/or how to point the application to the correct target link?

2. If that is not possible, do I need to download some version of the .net framework that the application is expecting to see? If so, how can I tell what version the application is looking for?

3. If the above solutions do not work. should I uninstall the visual studio 2010 that is on this workstation and reinstall a new version so that the application can find the correct version of the .net framework?

4. If you have a different solution would you tell me what I should do to solve the problem?