After many days of thought I have decided to change my Anti-virus from MSE to Avast!
This is my own choice and am currently happy with Avast!
However I was unsure how to uninstall one AV and install another so I'll say what I did and if what i did left me prone to infection.
At first I disabled MSE to prevent it saying Avast! while installing was a virus. I then installed Avast! and got it up and running and then I stopped and uninstalled MSE so it is no longer on my PC.