Summary: Still the workhorse for the MS OS choices. Faster than Vista or 7. Does not require the horsepower or memory as the newer systems, but will still run almost all the software.
Pros: Stable, robust, easy to use, proven features, small memory requirements, plenty of good software. Keeps older hardware running rather than becoming obsolete.
Cons: Vulnerable to attacks from worms and vurii, somewhat dated user interface, not well integrated with the most modern hardware. Can be a bit of a hassle to install depending on hardware. Anti-virus can rob XP-based systems of performance.