Everyone has heard about computer viruses and they are a big problem because they are written to spread through email or even from some web pages. The problem comes in when your anti virus software is not up to date so you don't even know. There are a couple of free for personal use pieces of software that I recommend
A few years ago a virus was normally passed around on a floppy disk. But with so many people using email now it is becoming a bigger problem than ever.
The first suggestion I would make is if you don't know the person sending the email...question it. It's a good idea not to open attachments especially from someone you don't know. If you use anti-virus software (you should) keep it updated (I update almost daily) and save any attachment to a temp directory and scan it before you ever open it. One of the problems with most email software now is that you can't even delete an email without the code running (you click on it to delete it and the virus tries to run). Your software should look at any file and not allow it to open if it contains a virus.
Even if the email comes from a name you know be careful because a virus will sometimes fake a from address. The thing to watch for there is "does it sound like the person?". I have received emails that seemed to be from someone I knew but it just didn't look like the way they would express themselves so I checked the attachment and sure enough it had a virus.
It is a good idea to do an online virus scan once in awhile. There is one program that catches almost everything. The online scan I use is