Windows XP build 2542

Windows XP build 2542 is a pre-RTM build of Windows XP. This build allowed using new types of product keys, and also extended the 14-day grace period of Windows Product Activation to 30 days.

Particularities
This build of Windows XP is rather particular. Considering it's a very near-to finished build of Windows XP, many programs that do work on XP do work fine here too.Things like VMWare Tools and UxTheme Patcher do work just fine (albeit an older version).

You can use this build with the current date by using TweakNT. The latest version of Firefox that's certain to work is Firefox 10.0.1.