To get emails is so great, but when it contains virus or worms, it's not that great, that's why I made this page, hopefully it can help a little.
Removal tools for some viruses and trojans, and here are more tools
Visit Windows Update frequently, there are the security patches for your operative system

Some viruses, like Klez takes addresses from the address book and from the Internet cache file. Then it use the addresses for both To and From -address when it spread itself.
So, if a person gets infected by Klez, and have your address in the address book, it can send infected emails to a lot of other addresses and make it look like it comes from your address. Klez can also send false replay mails making it look like a mail server is returning a mail you seems to have sent.
The worm can start automatically only by reading a mail so make sure your antivirus software is updated and download the security patches provided at Windows Update.

Due to a lack of security in IE you can get infected just by reading a mail, one doesn't have to click on an attachement. To prevent this you can download a security patch here

Virus are small softwares that hide in other softwares.
Some people think it's fun to deliberatley plant virus in software, when other viruses are bugs in the programmin process.
If you are infected by a virus it might happen that you get strange messages from your computer, crash or other bad things. The best way to avoid being infected is to be very careful with what software you install, and of course, to have a competent antivirus software, and update it regulary.

One has to be extra careful with files from the Internet, especially files coming in email and ICQ. If you are the least suspicious, don't open it at all, or at least have an updated antivirus software checking
it before opening.

What is spread on the Internet is computer viruses, macroviruses, worms, trojans and other bad programs noone wants to have in the computer. Most of these programs is named "computer virus", even if it's not always a virus.

A "trojan" is a software working two ways, a page is shown for the person starting the program, it can seem to be nice and safe.
But, there is another side of it, the main purpouse with the program: It migth be to open up security, as "Netbus" and "Back Orifice". it can install and spread virus, destroy files on your hard drive, or make
anything else one doesn't want to happen. 

The only way to feel a little more safe is to have a good antivirus software, and make sure to update it, I update mine at least once a day.

Whatch out for file endings as .exe, .vbs, it is mostly them containing viruses. 
There are virus codes written to change the file namn to, for example, .gif, but you can prevent this from happeing by chosing to show file endings for registrered file types. Just remember if you do so to write the file ending if you saver an image, .gif or .jpg.

A "hoax" is a false virus warning, and it comes once in a while, and are sometimes as dangerous as a real virus, the email itself can spread virus and worms.
Read more about Hoaxes here
Or here

On this page I have some links to free firewalls and to free software to remove spyware

Some antivirus softwares:

Microsoft Security Essentials - free

AVG - free

Panda Cloud Antivirus - free

Nod32

Kaspersky AntiViral Toolkit Pro

Symantec

McAfee

Microsoft's security page

Virus check with Panda online