How to prevent from virus?

These are best practices to protecting your computer/laptop:
Perform monthly updates of Microsoft patches
Perform daily updates of your Anti-Virus/Firewall program(s)
Perform daily updates to your Anti-Spyware and Adware program(s)
Perform a weekly scan of your hard-disk for viruses/spyware
Best of all know your computer. When you are connecting on a wireless network

- You see your hard-drive flashing solid green and you are not doing anything. Your computer/laptop may be infected.

Have two separate logins on your computer. One with admin rights and another with regular rights. Always use the login with the regular rights. If someone hacks in during your session. The hacker is limited to the account with regular rights and can't do much.

Always have a backup of your computer/laptop for restore purposes.

At the end it is up to you. Never visit sites that you don't recognized and don't trust your Emails. Always take it with a grain of salt.