We never had any problems to check such things for our machine, as life was too simple at the time of Windows XP. But with the gradual inventions in the direction of faster and better performing processors resulted in two different type of processors, one is the normal 32-bit and the other is 64-bit processor.
So firstly, lets understand a bit of technical information about this topic, what does it mean by 32-bit and 64-bit. These numbers represent the width of the Data Bus between the Processor and the Memory (RAM). In simple terms, there are two roads with equal distances connecting a source (your residence) and destination (your office) is 2-Lane (32-bit) and the other one is 4-Lane (64-bit).