You can get free anti-malware (anti-virus/anti-spyware) software here from AVG. Norton is a highly rated paid program. You will also receive free automatic updates that will include the latest virus/spwyare definition files. Microsoft Security Essentials also offers free anti-malware software, which includes free automatic updates for Windows 7 and Vista.
Microsoft offers a total of 6 free anti-malware programs. Each of them has different capabilities. MS's offering is extremely confusing. Two of the programs have the same name, but are very different.
You should run only one anti-malware program in real-time active mode on your computer. However, you can have multiple programs on your computer that run passively, i.e. you have to ask the program to scan your computer. Two example of passive anti-malware programs are Malwarebytes Antimalware and Super Anti-Spyware.
If your computer becomes infected with a virus, you may be unable to boot to Windows. If you have a rescue CD available, it may remove the virus and allow you to boot to Windows. Several companies will create free Rescue CDs. You will need to burn the Rescue CD to a CD. This free software can do that for you.
There are 3 companies in the world that perform ratings on anti-malware programs. The companies make their ratings available to the public. You can see the ratings from AV Comparatives, AV-Test, and Virus Bulletin. PC Magazine also rates free anti-malware programs, although their tests are very different from the three above.
You already have a one-way firewall on your computer. You may wish going to this website, where you can obtain a free firewall called Zone Alarm that is even better than the one that comes with Windows because it is a 2 way firewall. You can also read a review of Zone Alarm.
This web site allows you to see if your email address and password were among the 500,000,000 that have been stolen in the past few years. The New York Times offers this web site that allows you to see whether your credit cards numbers have been exposed to hackers.
The "bad guys" who try to break into your computer can use programs sold on the internet that crack passwords. Using a lengthy password makes it much more difficult for criminals to crack your password. You can learn how long it would take a criminal to crack your password. Recently a computer was built that can use brute-force to try 350 billion passwords/second. You can read reviews of 8 password managers including Lastpass, Dashlane4, LogmeOnce, and Keepass. You can also read this review of 10 password managers.
Most anti-malware companies sell 3 different versions of their software. For example, Symantec sells Internet Security Standard, Internet Security Deluxe and Internet Security Premium.
The Google toolbar contains a feature that blocks pop up ads and it is available free.