What programs do you recommend to protect Windows against all the problems? Or to put it another way, what do you have for your computers?
Bill Frost

There is no magic bullet, and things are changing. The biggest threat today is drive-by installation of malware from a website (read Google's The Ghost In The Browser: Analysis of Web-based Malware - it's a pdf). These sites try to exploit unpatched holes in the operating system, so the most important defence for most users is to have Windows updates installed automatically.

It's also essential to have a firewall installed, and to have at least one anti-spyware program. Windows Defender (formerly Giant Antispyware) and the free version of AVG Anti-Spyware (formerly Ewido) provide good defences. If you are willing to pay, pay for AVG Anti-Spyware and WebRoot SpySweeper. For antivirus protection, AVG Free and Avast! are good free scanners. If you are paying, go for Kaspersky AV or ESET NOD32. I also recommend running periodic checks with a different online scanner, such as Trend Micro Housecall or BitDefender. There are many others, including Panda ActiveScan, Kaspersky, Avast!, F-Secure, ESET and Symantec. It's worth trying a company's online scanner before you buy its software.

You can reduce your chances of getting caught by using a more secure browser. Opera is probably the safest, followed by Firefox and then Internet Explorer 7. If you want a more secure version of Windows, then 64-bit Vista is much the safest, followed by 32-bit Vista, then Windows XP SP2. You should also run Windows from a standard user account, not as an administrator.

Unfortunately, a lot of malware nowadays exploits users by social engineering rather than software defects. People are conned into installing malware by offers of fake antivirus checking or speed-up software, free music or pornographic videos that mysteriously require the installation of a new codec or ActiveX component. You can send people encrypted, password-protected viruses and they will still infect their own PCs. As a test, I've been running my always-on auto-updated desktop PC with IE6 and, later, IE7 with only a firewall and a NAT router. In almost two years, I have had only one minor exploit, which got me to install AVG Anti-Spyware. I also use SysInternals' Process Explorer and other software, so I know what my PC is doing, and can kill processes manually. This is definitely not a recommendation, but suggests that one of the most vital anti-malware defences is between your ears

The Guardian