|Run Malwarebytes to be sure there is no malware causing the trouble. If needed, download on another machine and save to a flash drive and copy it over to your desktop. If it wont install or run, try again in Safe Mode.|
Free version of Avast is a better option for an antivirus program.
Sometimes when programs are uninstalled, you need to restart to complete the uninstall in the registry, If you have not done this, it is worth a try.
Revo Uninstaller has a free version that is spoke of well here, it is worth the try to remove remaining traces of AVG.
CCleaner is considered safe here, even for registry checking. Worth the try also. (I have not used either of these but they are spoke of well by those I trust for advanced advice)
You have to be a little bit crazy to keep you from going insane.