Anti-Malware for Windows

Malware (adware, spyware, trojan, virus, worm) protection is now so essential for computers running Microsoft Windows that free trials of commercial anti-malware software (anti-virus, Internet security, etc) are commonly included in new computers. The catch, of course, is that they aren't free forever, and that they won't provide proper protection without regular ongoing updates. But not to worry, because excellent free protection is readily available, so uninstall those commercial products and use these free tools instead:

Microsoft Security

Microsoft now provides both good firewall (Windows Firewall) and good anti-malware (free Security Essentials for Windows Vista and 7, Windows Defender included in Windows 8). Notes:

• How to activate Windows Defender in Windows 8
• How to Add “Scan with Windows Defender” to the Context Menu in Windows 8
• Windows XP (and earlier) is not secure, should not be used. 

Supplemental

Enhanced Mitigation Experience Toolkit (EMET) is free Microsoft software that significantly enhances Windows security. Recommended for advanced users.

Since no anti-malware tool is 100% reliable, it's a good idea to supplement Microsoft security by periodically downloading and running a scan with one or preferably more (as no one tool is perfect) of the following:

1. HitmanPro
2. AdwCleaner
3. Spybot
4. Malwarebytes
5. Microsoft Safety Scanner