One of the nice things about Windows is that there is almost always more than one way of doing something.
If you have been using Windows Explorer to click on these files to get them to run I hope I am not insulting you if I say it takes a double click to start file running. If that doesn't work, have you tried using the 'Run' command ? If you click on the 'Start' button yu may see it already listed, otherwise click on 'Accessories' in 'All programs' and you will find it there.
Click on 'Run' to start it running, then 'Browse' to find your installer and click 'Open' then 'OK' and the installer should start running. And if that doesn't work, then RIGHT click on the installer in Windows Explorer and select 'Run as administrator'. One of these should work for you.
I can understand why you uninstalled AVG but this was not really the best course of action, you really should have AV available. However it is almost always possible to disable an AV product for a period. It's a while since I used AVG but if I remember rightly you could disable it for either a fixed period of time, chosen by you, or until you re-booted. This is a much safer way, and also much less work, than uninstalling and re-installing !