Here's a list of a few of the free downloads out there.
Freeware AntiSpyware and Security Programs
Software firewalls with freeware versions
Free Zone Alarm SE: http://www.lavasoftusa.com/support/download/http://www.zonelabs.com/store/content/comp...;NONE?lid=ho_za
All the above are superior to the Windows XP firewall because they protect against both incoming and outgoing threats. The Windows XP firewall gives you protection against incoming threats only.
Antivirus programs - freeware (you can only use one enabled and running resident anti-virus program on your computer at a time. More than one will conflict)
Avast Anti-virus freewarehttp://www.komando.com/bestshareware.asp
Anti-malware freeware (You can have as many of these resident as you wish. Generally there is no conflict between these and you should always run several consecutively in safe mode when possible)
*AdAware SE: http://www.lavasoftusa.com/software/adaware/
*Spybot S&D: http://www.safer-networking.org/en/index.html
*the above are the two most important to have!
Microsoft Antispyware Beta: http://www.microsoft.com/athome/security/s...re/default.mspx
Microsoft Malicious Software Removal Tool (Win XP and Win 2000):http://www.microsoft.com/security/malwareremove/default.mspx
AČ - Free from http://www.majorgeeks.com/download4281.html
. Run it, click Search for Updates, then click Scan.
CW Shredder removes some variants of spyware known as the Coolwebsearch Trojan. The Trojan takes advantage of a flaw in a key component of Windows -- Microsoft's version of the Java Virtual Machine -- to install itself via popups often found on porn and illegal software (a.k.a. "warez") sites. Run CWShredder after installing, and have it look for updates. Then click the "Fix" button, and the program will both scan and fix any problems it finds. If your system does not have this kind of spyware, it will give you the good news.
Microsoft Baseline Security Analyzer (MBSA)
MBSA is an easy-to-use tool designed for the IT professional that helps small and medium businesses determine their security state in accordance with Microsoft security recommendations and offers specific remediation guidance. Improve your security management process by using MBSA to detect common security misconfigurations and missing security updates on your computer systems.http://www.microsoft.com/technet/security/...s/mbsahome.mspx
Online Trojan scans here -http://scan.sygatetech.com/pretrojanscan.htmlhttp://windowsecurity.com/trojanscan
Web based online Antivirus and anti-malware scans: (these can be run regardless of whatever else you are using. You must use Internet Explorer to run these because most are based on Active X.)
Kaspersky Anti-Virus Web Scannerhttp://www.kaspersky.com/service?chapter=161739400#betatest
Windows Security Trojanscanhttp://www.windowsecurity.com/trojanscan/trojanscan.asp
Panda Activescan (IE only)http://www.pandasoftware.com/activescan/co...n_principal.htm
Trend Micro antivirus and malware scan:http://housecall-beta.trendmicro.com/en/st...orp.asp?id=scan
Etrust Anti-virus web scannerhttp://www3.ca.com/securityadvisor/virusinfo/scan.aspx
Windows XP Users:
Once you are certain there is no malware residing on your computer adding SP 2 will give you exponentially better protection against malware infection and is considered "CRITICAL" that you install it by Microsoft.