In Windows XP, users can find processor information, including architecture, by accessing the "System Properties" window. This can be done by right-clicking on "My Computer" and selecting "Properties," or by navigating to Start -> Control Panel -> System. The general tab displays basic information about the CPU, such as the model and speed, but does not explicitly state the architecture. To determine the architecture of a specific processor, users are advised to search online using the processor's model number. For more detailed specifications, including architecture, users can utilize third-party software like CPU-Z, which provides comprehensive information about the CPU, motherboard, and memory.