What programs do I have to have for my computer not to get screwed up?

Answer 1

If you mean basic "protection" utilities, you need

* firewall, to block hack attempts
* antivirus, to block e-mail and other viruses
* anti-spyware, to block spyware and such

If you just want ONE program that's easy to use, I'd say Norton 360.

Of course, there are still ways to mess up your computer yourself, but with these constantly updated chances are much less that something external will mess it up.

Answer 2

if you dont want viruses and spyware there are several free things i would go for. They do just as good a job as things like Norton but are free.
Firewall- Zone alarm
(http://www.zonealarm.com/store/content/catalog/products/sku_list_za.jsp?dc=56pus&ctry=GB&lang=en)

Anti spyware- Spy bot search and destroy
(http://www.safer-networking.org/en/download/index.html)

Anti virus- Avast 4
(http://www.avast.com/eng/avast_4_home.html)