Is your laptop underpowered? If you're not afraid to experiment a little, download and install a Linux operating system distro. Try Xubuntu if you're real familiar with Windows. I have it on my laptop and love it. It's made for older/underpowered computers. A resource minimalist operating system unlike Windows. It's also fairly virus resistant. Totally free too. You can install it on your computer in another partition and still keep Windows just in case you don't like it. It may resurrect your old laptop and keep some cash in your pocket to buy more saw stuff.
I started using a trackball mouse about 3-4 years ago because I was starting to develop pain in my wrist (it wasn't from any type of repetitive jerking motions). At first it's a bit awkward but now I LOVE it. You have to try one. I'm with you on a full sized keyboard. Just like the feel of them.
Edit: Or try out Zorin OS. I've never personally tried it but I heard it's setup to be a Windows clone. Only distros I have experience with is Ubuntu, Xubuntu, and Lubuntu. Ubuntu looked way too goofy for me. Lubuntu is even less resource hungry than Xubuntu but I find it to be a little more challenging for newbies.