So I have been trying to run a few programs that were built using the .NET 3.5 Framework. Every time I try to open the programs, I get a new missing DLL error. I don't really want to just download the DLL files from the web. Instead, I want to know what program/package I need to install to get everything to work on my Windows 7. There must be some Windows feature I need to enable or some redistributable I need to install directly from Microsoft, right?
Try to re-install the latest .net Framework
Windows 7 has the .NET Framework 3.5 SP1 built in, it's a component of Windows you can enable or disable. You could try going to:
Control Panel → Programs and Features → Turn Windows Features on or off
And disabling "Microsoft .NET Framework 3.5.1", clicking OK, then enabling the feature again.
If that doesn't fix it, you can try the system file checker by typing
sfc /scannow into the Start Menu search bar or the Run dialog box.