For basic security and update patches install Service Pack 2 for Windows XP or Service Pack 4 for Windows 2000.
Once a month uses Windows Update so you can get the latest patches.
When you download software from the Internet make sure you download it from the original website.
Always run anti Trojan and anti virus software.
Even if you don't use it you have to make your Internet Explorer as safe as possible.
When you access the Internet you are browsing the web using a browser such as Internet Explorer. The Internet Explorer contains several security vulnerabilities. You should make it as safe as possible or switch your default browser to an alternative. You will have to set some options from the Manage Add-Ons in the Internet Options. You will see a list of add-ons that can be activated or deactivated. If you see any unusual entries just deactivate them so you can be sure you don't have a Trojan/worm.
Under Internet Options -> Security -> Internet -> you will see the Edit Level. You should set it to high in order to disable most of the security threats.
Your Web Browser should be ok now. Let's see what we have to do from our email point of view.
Because it's built-in in their Windows system lots of users like to use Outlook Express for emailing. But it's a fact that it contains many security vulnerabilities so I advise you to use alternatives. If you use a web based Email (you can browse your email with your web browser) you can delete viruses even if you don't download them to your PC.
Make sure you have installed an Anti Virus for 100% virus protection. One that I've found to be very good and never disappointed me is the AVG Anti virus. If you take the time to regularly update it you will be safe enough with it.
Lots of people install Firewalls because they believe their Internet security will be higher. I personally disagree. If you do not know how to best configure it, and you have to know much about the tech behind it to do so, it will just make your PC slow and software not working. You can just use the Windows XP SP2 firewall for basic security.
All this tips should make your PC safer. I browse the Internet every single day for some time now and they worked great for me. I haven't met a virus/worm for some time now.
