There is a defragmenter and disk cleanup utility built into the operating system. But I also use CCleaner to clean my disk. I have read in many places not to use third party defragmenters as it sometimes won't touch files it's supposed to move or can move, and they can sometimes move files they aren't supposed to, although I'm not sure how true it is.
There is a plenty of free antivirus software, and Avast has a software updater section which I've used a few times and it works well and helps me recognize when I have out of date programs. For antivirus I use Avast, Malwarebytes, and Superantispyware. Windows 8 does an amazing job of installing updates for drivers and itself in my opinion.
Edit: The person who posted (as I was typing haha) is very correct, you have a large learning curve, but those are great places to start is at those tutorials.