The_Prophecy :
That depends on what changes. Swapping the motherboard by itself forces re-activation right away.
AFAIK, changing from a 3rd party volume license OEM MoBo as on a Dell system to a typical "home build" system does. But I have changed MoBos on home built systems "Distributor pak - OEM" w/o issue. Needed to change 6 of these to require activation ..... w/ XP anyway.
1. Display Adapter
2. SCSI Adapter
3. IDE Adapter
4. Network Adapter MAC Address
5. RAM Amount Range (i.e. 0-64MB, 64-128MB, etc)
6. Processor Type
7. Processor Serial Number
8. Hard Drive Device
9. Hard Drive Volume Serial Number
10. CD-ROM / CD-RW / DVD-ROM