This is a fast online virus scan provided by BitDefender - the scan takes a few minutes only. It works in Internet Explorer, Mozilla Firefox and Google Chrome on Windows XP, Windows Vista, Windows 7 and Windows 8. You need to launch Internet Explorer with administrative rights in Windows Vista, 7 and 8.
For Internet Explorer, an ActiveX control needs to be installed - Internet Explorer will warn you about this.
For Mozilla Firefox, an add-on needs to be installed and Firefox must be restarted after installation.
Instructions for Internet Explorer are provided below.
This virus scanner scans active 32-bit processes (running programs) on your computer and detects viruses and malware in them. It will not remove any of the possibly infected items, it just gives you a quick indication whether your computer is clean or not. So this is not a replacement for an anti-virus or anti-malware program!
You can see my recommendations on free anti-virus programs and free anti-malware programs.
Using BitDefender QuickScan in Internet Explorer
Windows XP users should just open the current webpage.
Windows Vista, 7 and 8 users must launch Internet Explorer with administrative (elevated) rights to install BitDefender QuickScan ActiveX control.
To do that in Windows Vista and 7, open Start menu by pressing Windows Key on your keyboard or by clicking Start button. Type "internet" into Search box and right-click Internet Explorer in search results. Click Run as administator.
In Windows 8, go to Desktop using keyboard shortcut Windows Key+D. Then right-click Internet Explorer icon on Taskbar, right-click Internet Explorer in the menu and then click Run as administrator.
User Account Control pops up. Click Yes or Continue.
Now open this same page.
Click the red Start scan button in BitDefender QuickScan window. If nothing happens during next 10 seconds, click the button again.
Internet Explorer 8 will display a yellow Information Bar after a while. Click it and select Install This Add-on for All Users on This Computer:
After another while, another warning prompt appears. As long as Publisher is "BITDEFENDER LLC" or "BitDefender SRL", you are safe to click Install.
Internet Explorer 9 and 10 users should click Install in the yellow Notification Bar.
After another while, User Account Control or Internet Explorer Security Warning appears. As long as Publisher is "BITDEFENDER LLC" or "BitDefender SRL", you are safe to click Yes, Continue or Install.
BitDefender QuickScan End User Software License Agreement opens. Click I Agree.
Now the scan starts. This takes a few minutes only. After scanning is complete, a report with active program names and their identification data will be uploaded to BitDefender for analysis and malware detection. The results will then appear after a few seconds.
Don't worry, the report includes no personal or otherwise sensitive data!
If no harmful programs were found on your computer, a success message will be displayed after this. You can feel a little safer now and navigate elsewhere. 
In case something was found, you will see a red cross mark and count of infected items.
If you are interested in what was found, click the red View log link.
This will open Notepad with the scan log. If long lines are not fully visible, click Format menu and click Word Wrap.
Steps to take if infected files were found
If your computer was not clean, you can install a free anti-virus program, for example avast! Free Antivirus or Microsoft Security Essentials and perform full scans. Just remember not to install more than one anti-virus program, as this will make your computer really slow.
Also make sure you scan your computer with free anti-malware programs, such as Malwarebytes' Anti-Malware and ComboFix to make really-really sure your computer is clean of all kinds of malware.
To prevent further infections, use the free WOT Safe Surfing Tool and Trusteer Rapport for keeping away from malicious and phishing sites; and use Secunia Personal Software Inspector to keep your programs up-to-date and secured.
