Microsoft Windows XP Professional w/ Service Pack 2 Review

Windows XP (especially the Professional edition) is the longest living OS from MS due to its stability, compatibility, and flexibility.

When compared to its predecessors (Windows 2000/ME) and successor (Vista), XP easily out performs them in every useful category (I will admit that Vista looks prettier, but since that doesn't make your PC run faster it is a non-issue).

Unfortunately, it will be almost impossible for you to find a copy now as MS has stopped shipping and stores are out of stock. If you need to replace your OS, hold out for Windows 7 (skip Vista... waste of money).