Monday, June 30th is the last day to buy the retail version of Windows XP. Microsoft will continue to support Windows XP until 2014 but users will no longer be able to purchase it with a new computer or in a retail store.
A little known loophole allows exists that allows end users to still buy Windows XP. Only the retail version has been discontinued. The OEM version sold to system builders will still be available for purchase and can be purchased by anyone that knows where.
If you built an low power computer and want to avoid Vista I have provided links below to where you can buy the OEM version of Windows XP Pro.
Update: The OEM version of Windows XP is no longer available. However, you can still find Windows XP for sale on Amazon and other sites: