having issues with Windows 7.

I am having all sorts of problems with Windows 7. firstly AVG free 2015 decided it couldn't find my licence number, I tried to re install AVG , but I got an error message saying windows installer was not working properly, Looked on AVG's own website and used their fix tool, that did nothing and now I cannot uninstall AVG or any other program. I have now discovered that I cannot launch Outlook either! Is my machine virused due to AVG not working, or do I need to repair Windows 7? I can't get Windows defender to work as a stop gap eother. Sorry this is a bit of a rant, but I've had enough!!