text: can we use the existing softwares and windows 2000 in 64 bit machines? how fast would be the 64 bit machines when compared to that of the present 32 bit machines? is it costly? using 32bit applications on 64bit machines ois no problem... 64bit-processors support 23 & 64 bit applications...  regarding the speed, it depends on the type of processor either intel or amd, and the type of task you want to do...  don`t expect both to respond similarly...to compare different 32 & 64 bit processors while doing different tasks (ex: compression, directx, etc) try visiting tom`s hardware  http://www.tomshardware.com/