Wish to purchase new license after motherboard change

I have a Compaq Presario CQ61 that has developed a motherboard fault. Currently intermittent but getting worse. I purchased a second near identical laptop (with a licensed and working operating system installed).

Rather than having to reload all the programs (they are extensive) and data and settings in the second computer as if it was a new installation, I tried removing the hard drive from the faulty laptop and putting it in the second laptop. That worked fine (a few driver issues etc that I fixed up) and the "new laptop" is fully operational.

I am aware that since both laptops have OEM versions of Windows installed, it is not possible to transfer the licence from one to the other. But I am happy to purchase a new license for the second computer to make it legal. In fact, I may at some stage try and fix the original motherboard so would like to keep the original license on this.

Is it possible to purchase a new license and activate what is otherwise a fully working functional laptop,
but has an operating system that does not now correspond to the motherboard hardware as regards license, without having to do a full clean install and have to start again from scratch setting it up as if you were starting with a new computer?

At this point in time the system is working but giving me a warning that it is not activated and will attempt auto activation in two days.

Thanks for welcome, and the tips Ranger4. I will phone Microsoft on their activation line as you suggest.

What I'm unsure of, is that if I do find and purchase a new installation DVD with license for Windows 7, will it allow me to install it without losing everything on the hard drive? If I have to do a clean install it defeats the purpose of what I have attempted/achieved in "transporting" everything from the intermittent laptop, to the replacement laptop by way of the hard drive.

It was actually more difficult than I first expected because what I didn't know when I purchased the replacement laptop was that it had Intel Chipset while my original laptop was AMD. It was a challenge and took more than new drivers, but I got there, so am now particularly keen to get it all completed with a legal license.