It is possible to get the key from a Linux live disk (e.g. a Ubuntu Live DVD
), or any linux system that has access to the computer's drive (booted from usb, dual booted etc) - this may also be possible from another windows system without third party apps (example). Then you can get the licence by:
Get a registry reading/editing tool. I used
chntpw, it is currently available in the Fedora and Ubuntu software repositories.
Get the registry data. You will need the file that contains the registry data from
HKLM\SOFTWARE, this should be located at
/Windows/System32/config/SOFTWARE (text case may vary, could be
/WINDOWS/system32/config/SOFTWARE etc). If you can read the hard disk this should be accessible
Extract the data. Run
chntpw with the path to the registry file - e.g. with the windows partition mounted on
chntpw -e /mnt/Windows/System32/config/SOFTWARE
And get the data from the
HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\DigitalProductId key - you may be able to use
dpi command, otherwise you can read the key data directly using
hex Microsoft\Windows NT\CurrentVersion\DigitalProductId.
If you don't succeed, you could check the hardware to see if it has the key embedded using the answers here. Or check for a sticker that came with the computer with the licence key written on.
Also if the Windows is a retail or OEM licence, you may just find a unique ID as the key is for use one time only.