I just found an article that explains how the hardware configuration works:
<What is significant?
In a PC that has a network card (used for corporate networks, home networks, cable modems, and DSL connections, for example), a significant difference in hardware configuration is:
changing the network card
leaving the network card alone and changing about six other components
In a PC without a network card...
changing three components
Also, OEM vendors selling pre-installed Windows XP systems will have the numeric code tied only to the BIOS of the motherboard. Swapping the motherboard with one from a different vendor will generate a significant discrepancy and require a reinstallation. Changing the motherboard is a common practice with engineers, corporate IS departments, and technically-adept home users..>
http://www.dgl.com/itinfo/2001/it010903.html
I'm not sure if this information is actually correct, but it sheds some light onto the situation.
-Kc2iLq