Virus protection 
The most important way to protect your computer from viruses is NEVER to let them in, in the first place.  If you stick rigidly to my rules for accepting attachments you will never have a virus!  Of course it is a good idea to have antivirus software installed to catch any viruses that do get in - there are many brands available, and some are free.  You have to decide which software to get, but whether it is free or top-of-the-range expensive  it is absolutely useless if you do not update it frequently.- at least once a week.  New viruses are being invented all the time and the software you downloaded even last week will not protect you from the virus that was invented yesterday.
Updating most antivirus software is very easy and does not take much time at all.  You can do automatic downloading with most reputable brands.  If you keep it up to date your antivirus program will catch any incoming viruses and you can fell secure.
Here are some antivirus sites to look at:
The two big names - McAfee and Symantec
A good free one - AVG Antivirus
The one I use - Computer Associates
If you suspect that you already have a virus on your machine, it is a good idea to do an online scan at Housecall to check it out and to deal with whatever the problem is.
Facts about computer viruses
Up until recently you could not get a virus just by opening or reading your email. Unfortunately this is no longer true - some viruses are embedded in the body of the email and do not need you to open an attachment to activate them.
This makes protecting yourself even more vital. First of all make sure you that if you have Outlook Express you have installed the available patch.  Go to
How to protect yourself
The first line of defence is not to let the virus onto your computer in the first place! It is a very good idea to examine your mail on your ISP's server before it arrives on your machine. I use Mailwasher , a free download.

By doing this, I can delete anything suspicious before it gets to the computer (and I can also delete or bounce any unwanted spam!)

There are threats not only from viruses.  Hackers and data thieves also lurk on the internet trying to get into your computer for one reason or another.  Because of this it is a good idea to install a personal firewall.  Two good free ones are Zone Alarm from Zone Labs and Tiny from  Tiny Software
 You can check your security and learn a lot more about it at Shields up!
Receiving attachments
Never ever ever open an attachment even if it is from your own mother, UNLESS she has had the courtesy to email you ahead to ask if you want the &^*&^ thing, and you know what it is and are expecting it.

Train your friends to warn you (or even better to ask if they may send it!)  That way you will not be opening a virus program that has sent itself without your friend's knowledge.
If you get something you are not 100% sure about, delete it at once.... and do not be tempted to peek.  If you think it is something you may want, email the sender to check on what it is.

Another reason to be very suspicious of an attachment arriving unexpectedly is if it comes on an email with NO message in it.  A good reason to be suspicious that it is a virus - would Mary Jane  not have put a "Hi Mum" message on her email??? 

If you do not have Mailwasher, and someone persists in sending you unwanted large files, set your message rules to delete these from the server.
And if anyone sends you spam, set your message rules to deal with it.
Web based email
This is a useful way to protect your own email address - use a web address when writing to an email list or leaving messages on message boards or other public places.  It can be a bit of a drag checking your web mail if you have several accounts.  Hotmail has a facility whereby it can be downloaded in your Outlook Express but I find it rather slow and unwieldy.  There are hundreds of other web based email facilities - EmailAddresses lists over 1000! 

If you use more than one you may like to look at ePrompter - the blurb says:

ePrompter� is a free email retrieval and notification utility that automatically checks up to eight password protected email accounts for AOL , AltaVista, Earthlink,,, Hotmail, Juno, Lycos,, Mindspring, MSN, Netscape, OneBox, POP3, Rediffmail, USA, Yahoo and hundreds of other email domains - all at the same time. It sits on your desktop and lets you know at a glance the number of new messages in each account, which you can easily read and/or delete online or offline with the click of an icon. It's extremely easy to set up and use.