How To Secure Windows XP
New PCs are usually more vulnerable to Internet and e-mail attacks. Before you connect your new system to the Internet, make sure that it is adequately protected with a firewall and that all windows updates and patches have been downloaded and installed. If you're using a home DSL connection, then some basic firewall capabilities should allready be provided by your DSL router.
It would, however, be safer if you also had a software firewall installed, just in case. Software firewalls can also protect from malicious software that may be operating on your PC, by preventing or at least limiting the communications these spyware programs may have with the outside world (e.g. sending data with your passwords or credit card numbers). Windows XP do come with a built-in firewall, and you should make sure that it is enabled, until you are able to obtain a better firewall product. Before Service Pack 2, windows had was was called the "Internet Connection Firewall" which was renamed to "Windows Firewall" after SP2. Windows Firewall is a lot better than the Internet Connection Firewall, but it still only provides protection from inbound traffic, which means that it won't stop a spyware program from sending data about your activities to it's creator. So, what you really need is an inbound/outbound firewall such as ZoneAlarm Pro.
Even if you have a firewall, however, you are not completely home free. You can still be attacked by e-mail viruses or web pages that exploit security holes in web browsers. To be safe, it's better if you first install an anti-virus suite and download the latest virus updates, before you start surfing the web. Notice that you should first download all updates and then start surfing the web. If your virus definition database is not updated with the latest viruses, this means that you can get infected and your anti-virus program won't even know something is wrong! The same is true for Adware and Spyware. In fact, these programs are effectively viruses with a different function. Don't get confused and think that anti-virus programs can detect and remove them though. You need to have one, possibly two anti-spyware programs installed in order to be truly safe.
Apart from using programs to protect your PC, there are some things you can do on your own. Windows XP allow two types of system access. Administrator access and limited access. System administrators can do pretty much everything to a PC. If you are infected with spyware, the spyware programs will run with administrator priviledges on the system. If on the other hand you access the system as a regular user (limited access) then spyware programs or viruses will only have limited access to your system. In fact, it may not even be possible for certain malicious programs to install themselves or other programs on your system, due to the limited access they will have. You can set up different user accounts from Control Panel - User Accounts. If limited system access causes problems for some of your applications, such as games, you can set these applications to run with the credentials of an administrators. Since you explicitly declare that on a per-application level, there is no danger of a spyware program or virus getting hold of administrator credentials. You can do this by right-clicking on the application's shortcut and selecting properties - advanced - run with different credentials. Bear in mind that you should do this on the application shortcut located on your desktop (so that changes will be local) and not on the application executable located in the program files folder. You should also use the system restore utility of Windows XP, to restore the system to a previous point of known safe functionality, should you get infected with viruses or malware and are unable to remove them.
As a final note, beware of naming conventions used by malware and viruses to try to fool you into opening and executing files. Unfortunately, windows tend to hide the extensions of known file types. So, if a file is named picture.jpg.exe windows will only show picture.jpg as a file name. While you might think that this is a JPEG picture and double-click on it to view the picture, this file is in fact an executable (.exe extension) which will run when you double click on it, and instead of a pretty picture, you get all the latest spyware on your PC. You might want to watch the icon next to file names, to make sure that it indeed corresponds to what the file claims to be (e.g. a picture) or disable the "hide extensions for known file types" options from the file manager.
James Hayes maintains the Anti Spyware Review page of InfoCastPortal