Manning - ASP.NET AJAX in Action Aug 2007, try this, i think it's good enough.

on xp it is very very big difference between 32bit and 64bit, xp 64bit runs much faster than 32bit on vista i found that 64bit is faster but not so much like the difference on xp, but, it's better to use 64bit, because you'll be safer from viruses, i even used 64bit without anti-virus for months, and never got infected, and i think that everyone knows how computers perform without antiviruses!!!