just so I’m sure, all I need for my household’s Windows 7 and 8 computers is what’s already on them?
W7 doesn’t come with MSE, it’s a separate download. But, yes.
And that’s a good question. There’s all manner of “total Internet security” type packages out there, some for a not inconsiderable amount of money. There are situations where something like this may be appropriate – I’m thinking hostile environments – but you’ve got to be a little sceptical when the people telling you to get this stuff are the people selling it. See the recent PC World thread.
The single most effective way of mitigating threats is to address the single biggest cause, and that’s the wetware sitting behind the keyboard. Not opening attachments in unsolicited emails, keeping software up to date, not clicking stupid shit on websites, not downloading executable files from .torrent sites, and reading software installers when they ask “do you want to install 37 useless toolbars from our partner?” will all go farther towards protecting your PC than any overpriced software.
What else do you need? Firewall? You probably already have two in place, one built into the OS and a hardware firewall in your router. There’s also various applications which go “are you sure?” when you click stuff, but nine times out of ten they just get annoying and people just blindly click “yes” out of habit. How would you reply to a prompt of “Application ‘commctl32.dll’ wants access to the Internet, allow? [Yes] [No]”?
MSE / Defender are both decent AV solutions which, unlike many others, don’t put your PC on its knees in the interests of winning comparison tests in magazines.