In plain English, a computer's IP address is similar to a mailing address. In order to send information to it, one needs the address. It is something you need, but also something worth protecting because it's possible for someone to scan your system for vulnerabilities IF they have your IP address and that can be a very bad thing if you haven't updated Windows with all the patches and if you do not have a firewall. I also highly recommend anti-virus, anti-trojan (sometimes AV covers trojans/worms but can't remove them), and anti-spyware.

Here is the link to download Ad-aware. This is a very effective free (for personal use) spyware detection and removal tool.

At the bottom of this page is a link to download AVG free antivirus. Try to use a "junk" email address that you never use when you sign up for it. I also highly recommend Symantec's Norton Antivirus, which is excellent but you have to pay to use it. Whatever you use, keep your definitions up to date (on both antispyware and antivirus applications) and run a scan weekly.

Here is the link to download ZoneAlarm; a free, very user friendly firewall. There are better ones out there, but this one is pretty solid and especially user friendly. Again, I recommend Symantec's Norton Firewall if you want to shell out some cash.

I'm sure others will give their input on what they like best and what you should/shouldn't use soon. Good luck.