In today's world of the Internet, a growing concern about Viruses have spawned to an all time high.
There are so many different types and ways of getting them. 
The Most popular way is from executing a file sent to you by email in an attachment.

The Best Advice I have on this subject is not to execute any file sent to you before scanning it with Some Virus Software. 

If you have no Virus Software you should delete the email and empty your recycle bin.

Do Not Open the Attachment If you can not confirm it is Virus Free, Even if it's from a friend.

Here are some Helpful Sites

http://www.symantec.com/avcenter/

http://www.centralcommand.com/

http://www.mcafee.com/

Thank you.
InterService Computers