Before I finally ditched Windows completely I ran my laptop for over a year with no anti-virus or 'internet security suite' whatsoever. I made sure the system was fully patched with updates at all times and that the basic XP firewall was switched on. I also practised 'safe surfing' - not opening any unexpected attachments or visiting strange websites. Problems encountered? None.
The way viruses, malware and other crap is distributed now has changed fundamentally from the old days, meaning that instead of viruses etc. trying to sneak into your system via infected Word documents or 'floppy disks' (ask your grandfather) they are now given permission to do so - by the user! A classic example of this is the various worms etc. doing the rounds on Facebook. A recent one was incorporated into one of those 'join this to see who's looking at your profile' things. When someone joined a worm was downloaded onto their PC. What makes this so difficult for 'internet security systems' is that the web page coding is done in such a way that, from the PC's point of view, you have given permission for the program to be downloaded and run on your system. The button may read 'Like' or 'Continue' but the coding in the background may be something far more sinister.
From a technical point of view it is very difficult for any 'security program' to work effectively when the user has given (unknowing) permission for something to be downloaded and run on their system. 'Safe surfing' is pretty much the only way to remain safe from the nasties that exist on the interweb. Which brings us to the dilemma - if you practise safe surfing then the 'internet security' software is unnecessary, if you don't practise safe surfing then the software probably won't help you much anyway!
Top Tips1 - Practise safe surfing. Be VERY careful on what you click. Don't open attachments unless you know what they are and come from a trusted source. Do not download anything you are not 100% sure about.
2 - See tip 1
3 - Do not use Internet Explorer - any version. Even the newest version has been found to have serious problems which, at the time of writing, are still un-patched.
4 - Avoid using MSN Messenger or Windows Live! Messenger. They have been a security problem since they were released. Trillian is a great alternative (
http://www.trillian.im/) and will still let you use your MSN account to chat to friends.
5 - Back up your important files. Regularly. A top idea is to start a Gmail account and e-mail your files to it from another account. Gmail gives you 8Gb of free storage which is a hell of a lot of Word documents etc. Also you can access the files from any internet connected machine.
6 - If you simply MUST have anti-virus/anti-malware then try Avast!
http://www.avast.com/en-gb/free-antivirus-downloadNB - If your using a Mac or Linux only points 1 and 5 apply.