The internet is an excellent tool, and no doubt has changed the way
most people communicate, unfortunately the internet, email in
particular, has created an easy to target medium for the spread of
computer viruses, as you have probably heard these viruses can cause
absolute chaos to whole networks of computers at a time.
A virus is basically a malicious computer program, the effect of
viruses differ, some either modify, delete or steal data and others
may give control of your PC over to their creators via the internet,
one thing they all have in common is that if you get infected and you
don't have antivirus software you might not know you have it until it
is too late.
A Worm refers to a virus that can replicate and spread by itself over
a network (the internet for instance), these are getting very common
and are among the biggest trouble makers on the internet.
A virus/worm can sit on your machine for months (potentially even
years) without doing anything and then be triggered by a certain
date/time to do what it has been designed to do, this is referred to
as its payload....

Registry Repair: http://groups.yahoo.com/group/regrepairsbv