let's get one thing clear... 64 bit refers to BOTH the operating system AND the hardware (CPU). eSignal is referring to the operating system. Win XP is 32bit Win XP pro is 32bit Win XP64 is 64bit Win VISTA Home is 32bit Win VISTA Ultimate is 64bit CPU: Core Duo is 32bit Core 2 Duo is 64bit 32bit operating system can run on a 64bit CPU