well i did upgrad mobo and prosessor but my product key stayed the last time i upgraded infact it activated auto matically
Waiting doesn't fix all...if it doesn't in your case type Windows Activation in Cortana and attempt to activate. It may/may not, in which case I suggest you use the phone activation option and talk to a tech. Tell them the story and they'll help you through it. I've done that a couple times and they've proven very helpful fixing up activation issues. In my case I had an OEM copy which is supposed to not travel to a new system...but since I'm the system builder, I'm the OEM and I can make a repair that consists of changing the motherboard and get a re-activation. The rep's understood that and helped me out.
And lastly, to completely avoid this in the future, get a Microsoft account and link your license to that account. Once you've got the digital license that creates you can activate your Windows easily by just using the Microsoft account to log on the system. Once done and activated with the digital license, simply change back to local credentials for logon and that's it. If it ever loses activation (it's never happened with me) just change credentials back to logon with Microsoft account and it fixes up automatically.
Of course, the activation will only work according to the terms of the particular license you have and your circumstance. But if you've a Retail license that's the best way I've found to easily upgrade systems without the hassles of failed activations.