Windows 8 -8.1?

[Radion]

1. Yes you should update to 8.1. Makes the OS much more bearable and improves performance a bit.

2. The free version of Malwarebytes is good for scanning when you request it to do so, but only the paid version will constantly monitor for malware. If you want a free program to supplement Malwarebytes with constant monitoring, you should get the free version of Avast. https://www.avast.com/en-us/index

3. If you want to make 8/8.1 more useable with things like the old start button, Classic Shell works wonders. http://classicshell.net/

4. There is no such thing as a random error unless a programer put one in as a joke. I might be able to offer a solution to get defender running if you post the content of the error. Even then, I would still recommend getting Malwarebytes and Avast.