Second time I changed motherboard, somehow I just activate as is with no hassle.
About 2 weeks ago I upgraded to W7 (funan $77), I decided to change my boot harddisk to something bigger so I re-installed vista first. Activate was also a snap. After that, I realize I have to install all the patches before I can install W7.. but that aside, it was smooth.
One thing I love about W7 is that SAFELY REMOVE HARDWARE now has volume name (instead of just drive letters in vista and xp). It is very useful for me since I have about 5 external harddisk, card reader and thumbdrive. Finally someone thought about that after 2 version upgrades.