Protect your computer from Virus or Trojans

1. Use a good anti-virus software:  There are several free anti-virus softwares available which provide good protection to your computer. Some such anti-virus are AVG free edition , Avast , Kaspersky etc.
2. Update Anti-virus virus definitions regularly : Most of users just install the anti-virus and they feel that that's all what is needed to keep the computer safe. But that may not be sufficient. You need to regularly update the Virus-definitions of the anti-virus software to keep them up-to-date so that your computer is safe from even the latest viruses.
3. Run full system scan every week: This is a good practice to run a full system scan using your anti-virus software at-least once in a week. This ensures that nothing goes un-noticed.
4. Scan removable drives for viruses before using: Scan your pen-drives and CDs / DVDs before opening them. 
5. Disable Auto-Play functionality for removable media: 
6. Run Internet Explorer /Firefox in limited mode : If you run Internet Explorer / Firefox with default settings, it has capability to install anything including viruses and Trojans on your computer. 
7. Don't open e-mail attachments from unknown people: This is one of the most common way of virus spreading. Not opening such attachments will save you from a lot of mess.
8. Disable preview mode in outlook / other email clients: We advice to disable the preview mode for Outlook / Thunderbird or other mail clients because of safety reasons. Let me put in simple words, when you open the preview, it will try to show all the content in preview, not even that, it will also try to execute any executable file if it is present as any attachment. So disabling preview mode can save you from such problems.