If the hard drive is still good then there are ways to “extract” keys from the drive. You would get a “utility” cd like “Hiren” or maybe others that are popular with techs.
Here is an example of using Hiren to retrieve a Windows key:
https://www.youtube.com/watch?v=gL93-jk5VqE
Your laptop would have to power on and the drive would have to be good for this to work. Otherwise if the laptop motherboard or power supply is dead and it wont power on at all then you could remove the drive and plug it into another computer and boot off the Hiren cd to retrieve your keys.
One of the other things i’ve had to do that you may is visit a bittorrent site to get a hold of an OS cd to use and then if the cd image you get embeds a key in its installer you just change the key to yours later as needed using a key changer utility. All this stuff can be learned by good web searches and reading.
thanks