Must Have Free Windows Security Apps for New or Old PC

Anti Virus:

Avast Anti-virus Home edition is non comercial and home user users. It got built in anti-spyware and anti- root kit protection. Registration is required to get the Key.
Alternatively, AVG Anti-Virus 9.0 Free Edition is free for the home users, registration is required. It also have anti-virus,spyware protection and email scanner.
Windows also have released Windows Security Essentials, free anti-virus protection for the PC. It is very easy to use than Avast.

Firewall:

Zone Alarm is a award winning firewall, it gives basic firewall for personal use. It blocks hackers and spyware access attempts. Automatically makes your computer invisible to anyone in the internet. If you use Avast Anti-Virus along with the Zone Alarm, you might disable the web shield protection in the Avast, as it might interfere with Zone alarm.

Alternatively, you can Comodo is also another award wining Firewall, along with free anit-virus it protects your PC from malware, viruses, worms, and more.

Spyware:

Spyware Terminator is free spyware removal tool with 100% real time protection and HIPS protection. It givers user to schedule scan the PC and updates are automatically  updated. It also comes with free anti-virus ClamAV, it is optional for the user to install.

The above security apps are more than essential for a PC.


Root Kit:

F-Secure Blacklight Rootkit Eliminator scans your PC and detects objects that are hidden from users and security tools and offers the user an option to remove them. The main purpose is to fight rootkits and all kinds of malware that use rootkits. The F-Secure BlackLight Rootkit Elimination Technology works by examining the system at a deep level. This enables BlackLight to detect objects that are hidden from the user and security software. For advanced users only.

Malware, Trojans and Unwanted Programs:

HijackThis scan your computer to find settings changed by spyware, malware or other unwanted programs. HijackThis is a free tool from Trend Micro which  generates an in-depth report to enable you to analyze and fix your infected computer.

Firefox Security Extension:

NoScript provides extra protection to your Firefox. It allows JavaScript, Java and other executable content to run only from trusted domains of your choice, e.g. your home-banking web site, guarding your "trust boundaries" against cross-site scripting attacks (XSS) and Clickjacking attempts, thanks to its unique ClearClick technology.

Adblock Plus you block any ads and banners just right clicking and choosing "Adblock" from the context menu - the banner won't be downloaded again.

Online Scanner:

Kaspersky Online Scanner will be checked for viruses, Trojans, spyware or other malicious code and provide the comprehensive report. You can then you the free virus removal tools to eliminate the viruses.

F-Secure Online Scanner is  can help get rid of viruses and spyware causing problems on your PC. It needs IE or Firefox. You remove virus from Easy Clean or other Free virus removal tools.

HouseCall is Trend Micro highly popular and capable on-demand scanner for identifying and removing viruses, Trojans, worms, unwanted browser plugins, and other malware. Fast scans that target critical system areas and active malware. It also leverages the Trend Micro Smart Protection Network™ to help ensure that scans catch the latest threats. Provides a full system scan option and an option to scan only specific folders.

ESET Online Scanner is a user friendly, free and powerful tool which you can use to remove malware from any PC utilizing only your web browser without having to install anti-virus software. ESET Online Scanner uses the same ThreatSense® technology and signatures as ESET Smart Security/ESET NOD32 Antivirus, and is always up-to-date.