You may have Antivirus, Firewall, Internet security, Anti-spyware etc installed on your Windows powered computer. But if you want to further improve security of your windows, you can try a free tool from Microsoft, Microsoft Safety Scanner
What is Microsoft Safety Scanner
The Microsoft Safety Scanner is a free downloadable security tool that provides on-demand scanning and helps remove viruses, spyware, and other malicious software.
Can I use it with any Antivirus installed?
Microsoft Safety Scanner works with your existing antivirus software. So, you can install and use it even if you have Antivirus, Firewall, Internet security, Anti-spyware etc installed.
The Microsoft Safety Scanner is not a replacement for using an antivirus software program that provides ongoing protection. Please note, it do not provide any real time protection. It only scan your files for virus, spyware, and other malicious software and remove them.
Note: The Microsoft Safety Scanner expires 10 days after being downloaded. To rerun a scan with the latest anti-malware definitions, download and run the Microsoft Safety Scanner again.