As you may be probably aware , the support for Windows XP officially ends on 8 April 2014. As a user , what does it mean to you? I will try and answer few of those questions:
Post 8 April 2014, any security vulnerability which is discovered , will not be patched. So the unpatched Computer will be open to infection . And an infected machine will then most likely infect other Computers in the network.
So if your Computer is in a network or is connected to Internet , then using such a PC is a big risk. However , if you are not connected to the Internet and working as a Standalone PC, then the risk is minimal.
You may say that even if Microsoft does not issue a security patch , you have a third party anti virus to protect you. The bad news is that these products will not be tested for XP.
Your other applications also will not be tested for XP post the deadline. So over time, the XP machines are likely to become unstable . And new applications will simply not work on XP.
You should consider to move to a current computer with a current operating system. And with imminent launch of Windows 8.1, it will be the ideal time to upgrade your PC . Of course, you do have Windows 8 PC available even today. In fact , more than 100 million Windows 8 licenses have been sold so far.
However , if you are still reluctant to dump Windows XP, then at least ensure that
a) It is not connected to Internet
b) It is not connected to other computers
Wish you Happy and Safe Computing !
with warm regards