Goodbyes are always tough. And today we say goodbye to a dear old friend, Microsoft Windows XP. Kind of. Today is the last day to buy Windows XP from retail channels, but many notebook vendors with the help of Microsoft will still offer Windows XP on select systems. Mostly thanks to the ill-received successor, Windows Vista, Microsoft has agreed to keep XP running in certain situations. Earlier we put together a full FAQ on the future of Windows XP. The key takeaways: Windows XP will still be available from PC vendors as a “downgrade” option from Vista Business and Ultimate as well as on mini-notebooks. Because Vista is just too chunky to run on a mini-notebook, like we saw with the HP 2133 Mini-Note, XP will continue to be sold on what Microsoft calls ULCPCs (ultra-low-cost PCS) until June 30, 2010. Mini-notebook lovers can only hope that Microsoft replaces Vista with a less chunky operating system by 2010. Something tells me Windows 7 won’t be the answer. Maybe by then we won’t need an OS, and we can simply live in a Linux system or even in the Cloud.