#1: Secunia Personal Software Inspector

Quite possibly the most useful and important free application you can have running on your machine.

It can be used to scan all the installed applications on the to determine which programs are missing patches/updates.

The tool works by by examining files on your computer (primarily .exe, .dll, and .ocx files) for meta information on specific software builds installed. After examining all the files on the machine, the collected data is sent to Secunia’s servers and matched against the Secunia File Signatures engine determine the exact applications installed on your system.

It can be used to flag insecure/end-of-life software and find direct download links to missing security updates.

It monitors more than 4,200 desktop applications.

#2: OpenDNS

Must-have free service (there’s no software to install) that speeds up Web , corrects domain typos on the fly and protects you from phishing scams.

All you do is change your DNS settings (instructions here) to the OpenDNS servers: 208.67.222.222 and 208.67.220.220

OpenDNS also offers parental controls, shortcuts and other nifty features to help with safe and reliable browsing experience.

#3 AVG Anti-virus Free Edition

The most popular free solution available at no cost to home users and provides the high level of detection capability that millions of users around the world trust to protect their computers.

#4: Haute Secure

A browser plug-in currently available for ’s Internet Explorer that does realtime blocking of drive-by malware downloads.

The tool, the brainchild of for ex-Microsoft staffers, fits behavior-based profiling algorithms into the browser (Firefox support is coming soon) to identify and intercept malicious files in real-time.

#5: GMER anti-rootkit

A free rootkit scanning tool built by Polish Windows internals guru, is widely hailed as the best at ferreting out stealth rootkits from PCs.

GMER does an excellent job of finding hidden processes hidden services, hidden files hidden registry keys, hidden drivers and all kinds of driver hooking.

It can also serve as a process explorer to monitor the creating of processes, the loading of drivers and libraries and file function and registry entries.

#6: Netcraft Toolbar

Powered by an active online community, the free toolbar is effectively a giant neighbourhood watch that helps you spot phishing and other identity theft schemes.

It provides a direct glimpse at the hosting location and Risk Rating of every site you visit.

The Netcraft Toolbar can also trap suspicious URLs, enforce the display of browser navigational controls (toolbar & address bar) in all windows, to defend against pop up windows that attempt to hide the navigational controls.

#7: File Shredder

A must-have privacy tool that wipes/destroys documents beyond recovery.

With File Shredder, you can choose between 5 different shredding algorithms, each one gradually stronger than the previous one to get rid of files forever.

#8: CCleaner

This free system optimization and privacy tool can be used to remove unused files from your system — allowing Windows to run faster and freeing up valuable hard disk space.

CCleaner also removes temporary files, URL history, cookies from the three main Web browsers (IE, Firefox and Opera).

It can also be used to delete temp files and recent file lists for all those third-party applications sitting on your PC.

#9: PC Decrapifier

Removes crapware that comes pre-installed on Windows computers.

This program will not remove crapware from older computers but is perfect for new machines that ships with trialware.

There is a long list of products it will find and remove, including QuickBooks Trial, NetZero Installers, Earthlink Setup Files, Desktop and the myriad of anti-virus trialware apps.

#10: NoScript for Firefox

This must-have Firefox extension does preemptive blocking malicious scripts and allows JavaScript, Java and other potentially dangerous content only from sites you trust.

Also blocks blocks Flash and other potentially exploitable plugins too, and provides the most powerful Anti-XSS protection available in a browser.