few hours ago my windows 8.1(single language) was activated. my windows came in pre-installed with my laptop.

Now it is asking me to activate it again or could not find cd-key.

please help.

Run this in an elevated command prompt:

Licensingdiag.exe -report %userprofile%\desktop\report.txt -log %userprofile%\desktop\repfiles.cab

and post the contents of the report.txt it makes on the desktop.