The NSA (National Security Agency), which normally deals with intelligence activities (roughly the Swedish FRA), has released a user guide that describes how internet users can improve their computer use and their security on the internet.
The guide named Best Practices for Keeping Your Home Network Secure can be downloaded as a pdf file from the NSA website. The guide is written for private individuals and is relatively easy to understand.
One of the recommendations the NSA makes in the guide is that users should run Windows 7, or even Windows Vista. Users of Windows XP should, according to the NSA, strongly consider upgrading to a newer operating system.