One way of keeping your computer safe from viruses and other malwares is to disable autorun especially so if you use USB flash drives to store files more often.
USB flash drives nowadays are the number one source of computer viruses which are easily transmitted from one machine to another. One of the threats is Long Live Sowar Virus. View the guide on how to defeat sowar.vbs virus.
Your greatest defense is to have a very effective anti-virus installed in your system. Next to that is to disable the "autorun" function of your operating system.
How to disable autorun:
1. Windows XP Pro users: Click Start and then click Run. Type gpedit.msc and click OK. The Group Policy window will open.
2. In the left pane, double-click Administrative Templates. In the right pane, double-click System, scroll down the list and double-click Turn Off Autoplay.
3. In the Turn Off Autoplay Properties window, select Enabled.
4. From the dropdown next to Turn Off Autoplay on, select All drives and then click OK. Exit Group Policy by selecting File, then choosing Exit from the menu.
5. XP Home users will need to make the changes by editing the registry directly. To begin, click Start and then click Run.
6. Type regedit and click OK. The Registry Editor window will open. In the left pane, navigate to:HKEY_CURRENT_USER\Software\Microsoft\Windows\7. With Explorer highlighted, in the right-pane right click the value NoDriveTypeAutoRun and select Modify from the drop down menu. The base value will be set to Hexadecimal. If not, select Hexadecimal. Type 95 and click OK.
CurrentVersion\Policies\Explorer
8. Note that this will stop Autorun on removable/USB drives, but still allow it on CD ROM drives. If you want to disable autorun on both, substitute b5 for the 95.
9. Exit Registry Editor by selecting File, then choosing Exit from the menu.
10. You will now need to reboot your computer for the changes to take effect.
Source: About.com