The number of bits in a processor refers to the size of the data types that it handles and the size of its register .A register is a small amount of memory available to the processor in order to speed up its operations.Thus,a 64-bit processor can address a larger physical memory locations and hence,can handle larger amount of RAM, than a 32-bit processor. Another difference is the speed .A 64-bit processor can perform more number of calculations per second than a 32-bit processor.Windows 95, 98, and XP are 32-bit operating systems and Windows Vista, Windows 7, and Windows 8 are 64-bit. A 64-bit machine can have a 32-bit or 64-bit operating systems installed on it whereas a 32-bit machine cannot have a 64-bit operating system installed. Although it is possible for a 32-bit software to run on a 64-bit machine,a 64-bit software cannot run on a 32-bit machine. How to find out whether a computer is running a 32-bit or 64-bit version of windows? Right click My Compute...