I use Zone Alarm on my laptop... Antivirus plus Firewall (which is fairly common thee days). I think the paid version costs about 30 for 3 licences... i.e. you can install on 2 other computers if you have them (again quite a common feature these days). There is a free version too but probably with limited features.
I use the free version of Avast on my Android tablet and don't have any issues with it. Although you have to root the tablet to be able to benefit from the Firewall. No viruses reported on my tablet so far so in truth I don't know if it is stopping anything or not. But it gets good reviews, so I will stick with it for now.
Finally, SheSpoke and Daughter no 1 use Norton... (I'm not that keen on it... not sure you can get into the nuts and bolts of things in a the same way as Zone Alarm, but I'm told it is ok).
Oh and Finally, Finally... Checkout Ccleaner if you are having problems with clutter and also SuperAntiSpyware to clean up your system and remove adware etc. Both come in free and paid version but be sure to get all of your security software direct from the source (i.e. not from some 3rd party download site) particularly if you are going for the ShareWare versions