My grandfather is pretty tech-savy for his age and loves to send emails, use Photoshop, and browse the web. I've made his computer pretty secure by installing AdBlock and teaching him how not to download viruses but every once in a while he receives a flyer in the mail with a free trial for 'Avast antivirus'. He's the type of person who can't resist free and promptly installs it. This is pretty annoying because it slows down the computer a lot, prevents Firefox from opening, and does all sorts of other this-antivius-is-basically-a-virus things. It's also a real pain to uninstall.
My question: Can I set something up that prevents him from downloading, installing, or running an Avast installer?
I have Windows 7
Best Answer
If you want to prevent a specific software from installing, you can try importing its certificate (digital signature) to "Untrusted certificates". Then whenever he tries to install it, the UAC dialog will show "This software is untrusted" instead of prompting you to grant Administrator access to the installer program.
There is a safer way to use the installer's certificate, but may slow down the whole system by a little. You can import Avast's cert into the Group Policy, so even if it doesn't require Admin privileges, it won't run.
If you want to block all software installation, then give him a User account (without Admin privileges). It could be the only solution for blocking everything, though. You need to ensure that your grandfather doesn't need Admin privileges frequently.
If it allows, you can configure your current AV software so that it distrusts Avast's certificate, and may delete the installer immediately he downloads it. This is also a good option.
Anyway, I personally believe that educating your grandfather to learn to resist ads and those whatever free trials is the ultimate solution. Then you won't have to bother with this and that to prevent him from installing them.