Microsoft does not count it quite that way. A new mobo is not "counted".
It is certain hardware characteristics, some of which are on the mobo, that
are counted. It is a ten point system, with the accumulation of seven
points changed that triggers reactivation. At the time of activation, the
wizard generates a hardware hash that incorporates, among other things, the
hardware characteristics. The following is from:
http://support.microsoft.com/default.aspx?scid=kb;en-us;302878#5h
The 10 hardware characteristics that are used to determine the hardware
hash.
The following 10 hardware characteristics are used to determine the hardware
hash:
. Display adapter
. SCSI adapter
. IDE adapter
. Network adapter media access control address
. RAM amount range (for example, 0-64MB or 64-128MB)
. Processor type
. Processor serial number
. Hard disk device
. Hard disk volume serial number
. CD-ROM/CD-RW/DVD-ROM drive
Note: Only the system drive is checked. Only the first cd/dvd drive is
checked. Ram is considered changed if the amount of ram changes by at least
64MB, but changing by more than that does not matter. Once one of the
hardware items changes, that hardware item is not counted as changed again
no matter how much swapping you do until reactivation writes a new hardware
hash. You could try out five video cards and it would only be one item
change (the first change sets the flag but further changes have no
additional effect.) You can change up to seven characteristics before
reactivation is triggered.
So if a lot of the items are built into your mobo, changing the mobo will
probably trigger reactivation. If your display adaptor and NIC are cards
and not integrated on the mobo you might not have to reactivate. In any
case, as you can see from the list, the mobo itself is not a hardware
characteristic.