I find that all of these programs really never necessary for computer health anymore. Just follow some best practices and you'll be fine.
1.) Get an internet security suite. These are combinations of spyware protectors, firewalls, and antivirus. Usually, you get what you pay for, so free ones are okay, but paid for programs like Kaspersky, McAfee, or Symantec have a MUCH better detection rate. AVG is very popular, but it only has a 88% detection rate. That's 12% too low in my opinion.
2.) Defrag of your hard drive is okay, but can also reduce the life of your drive if done too often. No more than once per month is sufficient. It really thrashes the actuator arm.
3.) Know what you are installing, and remove programs you no longer use. This helps with system bloat over the years. The more fonts, and other things cause your system to slow down over time.Just keep what you use. You can always find what you need again, and re-install if you remove too much.
4.) Keep your machine updated all the time from Microsoft update. Be sure to also update Microsoft Office if you use that too. You'll need Internet Explorer for this.
5.) Choose a different browser for most of your surfing. Internet Explorer is okay, but the bulk of the vulnerabilities in windows are exploited through this browser. Firefox while nice, is not that far behind IE now too. It is still is more secure. Opera is a mature and very secure browser that works with 99% of the websites. If it doesn't work in opera, you can always use IE to open the site. I mostly use Opera myself. Google Chrome is also a very good browser, but can be a bit of a memory hog.