looking for some legal way to get my windows back on it. Lost product key

check the back of laptop
cdkeys usually located on that

There is a sticker there for product key, but its so worn off.

Any other tips

Define Broke.

The harddrive is making a clicking noise and unable to boot up the computer.

If you find another shell you could in theory try swapping platters to it.
Not an easy task but can be done. It's legal but costs a fuck ton to get others to do it for you.

So cheaper to buy new key. Cause time/risk/spare parts/cost.