The highly optimized XP Pro on my ThinkPad was the snappiest feeling OS I had ever tried until recently. Using nLite to only install what was relevant, turning off a lot of services that I did not need, and partitioning the HD to ensure that the OS was installed on the outer 20GB of the disk took me about a week of work, but resulted in a very fast and stable system. It even outperformed Ubuntu 7.10 and 8.4, although they were "stock" installs. (I have not tried 8.10 yet.) If I had compiled them for my laptop and otherwise spent the same amount of time I spent with XP, that might have changed. I hate Vista, but had been reading good things about the performance and stability of Windows Server 2008 when converted to a workstation, so I gave it a try. I downloaded an evaluation copy and installed it on the only free space on my drive, which is the slowest inner 25GB. After following all the instructions available on the Internet, I had an OS that outperformed my XP Pro installation on everything except startup time--even with Aero fully enabled. All of my applications ran fine on the 64 bit version, except for a couple of drivers--Bluetooth drivers required minor modification and the Bluetoth PAN did not work at all, and no drivers for my Globetrotter 3G card would work. I switched to the x86 build, and after making similar mods to the BT drivers, everything works great. It even supports my full 4GB of RAM. With a lot of copying back and forth to an external drive using dd, I managed to move my OS to right after the XP partition. I am still triple booting a couple months later in case I run into problems with a seldom-used critical app, but have not booted into XP in weeks. It is truly what Vista should have been--and could have, since it shares the core with Vista SP 1. However, I won't pay $500 for it. If you don't have or know someone with an MSDN subscription and are not a college student who has access to the DreamSpark program, it is probably not a viable option.
