What are some ways to prevent spy ware or virus from getting a computer?

There's a lot you should do, & most of it has been covered, but a major way of getting infected is downloading programs, etc from the wrong places. Always make sure the site is Trusted & virus free. It's better to "Save" the download to your desktop, than install it (that's when you click "Run"). After the download, before installing it, scan it with your antivirus program & any other security program you want. (I only choose "Run" from certain sites, like Microsoft & one or two more, that I know are safe)