Actually, if you're using your WIN XP system to regularly access the NET, than I would consider switching to Comodo Internet Security Premium(CIS) which is Free. It's only slightly more taxing on systems than Microsoft Security Essentials, about the same as Avast in WIN XP according to AV-Test.org.
CIS includes a powerful firewall, but its most useful feature may be its sandboxed desktop called
Virtual Kiosk. When clicked, it loads your browsers into an isolated desktop environment. So malware cannot make permanent changes to system or application settings, or permanently store files.
You can also run most any application in the Virtual Kiosk. CIS even gives you a right-click option in Explorer to run an application in Comodo sandbox.
The sandbox option is also useful for testing a new utility or app to make sure it doesn't contain malware, spyware or tracking, or unwanted third party programs such as browser hijacks. It it does, than just clear the virtual desktop, and start a new one which will load your browsers and apps with default settings intact.
If sandboxing an "unfamiliar" app you downloaded, make sure to use "full virtual" option, or run it in the Virtual Kiosk which isolates it from your system.
CIS options can be daunting, but most don't have to make any changes to its default settings. However, you may want to get rid of the desktop status widget which I find distracting. Just right-click and un-check "Show" to hide it.