Since April of this year, Windows XP SP2 has been in the extended support stage, which means support with Microsoft is no longer free and only includes security updates and patches. Next July (2010), XP SP3 will enter extended support as well. All support for Windows XP SP2 and SP3 will end in April 2014.
The ability to buy Windows XP machines will change now that Windows 7 is available. With the release of Windows 7’s first service pack, scheduled to be a year or so after its initial release, OEM licenses (i.e. licenses that are pre installed on comptuers) will no longer have downgrade rights to XP.
This means that to deploy Windows XP on a new PC, companies will have to purchase volume license copies of Windows along with the new PCs or use existing, unused Windows volume licenses.