Microsoft released one of the final interim builds of Windows XP that's expected before Release Candidate 1 (RC1), a build which includes the new Windows Messenger client that the company announced earlier this week. More importantly, however, is the fact that this release--build 2481--marks the finalization of the Windows XP user interface. This means that the Windows XP UI will not change between now and the final release. Changes with this most recent build include two new color schemes, Metallic and Homestead, which build off of the default Windows XP visual style (code-named Luna), and various other small refinements. In addition to the UI freeze, build 2481 also marks the point of no return for hardware compatibility: Though this build doesn't contain all of the hardware drivers that Microsoft intends to ship in the box with Windows XP, the company does not intend to add device support beyond that which is currently planned. Microsoft expects to ship RC1 the week of June 18, and this release will go out to hundreds of thousands of Preview Program customers. A smaller RC2 milestone is expected in late July, with the final RTM (Release To Manufacturing) code due in August. Windows XP will hit retail stores in late October, but PC makers are expected to begin shipping XP-based systems as early as September.