Laptop HDD replacement no image/backup

Hello all, first off let me say I am not 100% sure where to post this in the first place but I thought here is at least a start.

My wife rendered her laptop without a working screen a little while ago which I replaced. But her HDD now will not boot or even read on a all in one HDD reading device. So i cannot access the info on it. I was dumb and did NOT make a image/backup of the drive. Warranty is out. I have a brand new HDD (same make and model) but do NOT have a legal copy of Windows 7 (business I think was on it).

I am somewhat at a loss as what to do.

My buddy suggested 'getting' a copy of Windows 7 and the using a CD key changer to make it match the one on the back of the laptop but I was hoping there was something to do more on the legal side of things and still not pay any more money. It is not a very expensive laptop and I have already almost doubled its cost replacing this stuff.

Thank you very much for your time and have a nice day!