Do I need to reinstall Windows after changing Motherboard ?

[Mukachaka]

I changed Mobo to new one (same model). Should I reinstall WIndows ?

 

[USAFRet]

I changed Mobo to new one (same model). Should I reinstall WIndows ?

Exact same model? Probably not.

Is the OS still activated?

 

[Mukachaka]

Yes. It's exact same model because I purchased same two mobos..
OS is still activated as if there was no any change...
If I do not format pc, it may cause problem on the new mobo ?

 

[USAFRet]

Yes. It's exact same model because I purchased same two mobos..
OS is still activated as if there was no any change...
If I do not format pc, it may cause problem on the new mobo ?

There will probably be no issue with the new board.

 

[Karadjgne]

The biggest reason to reinstall windows after a mobo change is the mobo drivers. Things like Sata, USB, Lan, audio etc are all different, for different boards, especially for different brands or series. This can and will create conflicts with bunches of drivers active all trying to be noticed by windows, who has no use for them. A reinstall of windows wipes out the old mobo specific drivers and allows for a clean install of new ones.
Since you are using the same board, with the same drivers, same everything, it'll all work as prior since the drivers are all the same. Basically, according to your pc, nothing has changed but the serial number to the mobo.