Its a good Idea to further protect your computer more than the computer defender in control panel .If you havent got a system installed its a good idea to source one .
There are lots of different systems ,most you need to pay for total protection ,there are a few with basic protection free. Spybot search and destroy is one and AVG also has a free edition have a look and see what you think.
When using things off the internet read peoples reviews about different products before you buy anything.
Double everything onto another external harddrive ensures you dont lose everything if something goes wrong with your computer.
Take care opening emails ,only open trusted sources and junk the rest.
Use one of your emails photo gallerys to upload photos to so you can never lose them.
Use system restore on your computer to every few months to create a new restore point .
Using your computer tools in accesories cleanup and defragment every few months .