ok Lets cut the bullshit and point the factz..
No matter what ever you say it's definitely faster than Vista and Mac OS X for that matter, and even some Linux Distros (sorry to say this but Ubuntu Hardy is slower than XP...Use LinuxMint if you want a Lightening fast Ubuntu Derivative Distro). The reason XP is faster than is very simple, Its code base is more mature than Vista, and XP runs far fewer amount of background services Unlike vista, in all senses Vista is bloated with lumps of unnessasary software (sorry but Aero is one of them) On the original version of vista the Netwrk stack was utter rubbish but they have fixed it very nicely on SP1 so now its even faster than XP, but still even with SP1 vista runs programs far slower than XP. With the SP3 of XP they have fixed a lot of multi Threading capabilities and that contributed to some 10% performance increase with the SP3. Windows XP ports a Hardware compatibility that can rival any other OS (Thats what happens when a OS is arround for 7 years without a sucsesser lol but still its a fact). i can go on like this..but in reality only thing that really makes a difference about Vista is Direct X 10...if microsoft released DX 10 to XP we wont be even having this conversation cuz all of u will be runing XP without even looking at VIsta, And who says Games are Faster on Vista...every game is slower on Vista than on XP..Prove me Wrong.
All in All Windows XP is the best Microsoft OS one can stick Arround for the time being, Im not sure if another Service Pack can Fix vista as it is, but i have a little hope for Windows 7, who knows MS will come to senses and make it a good product.