That's why people have so many issues with Vista - You don't run software on hardware that can't take the heat. If you know your hardware can't run it, don't put new software on it and then say the software sucks. Most new PCs will be able to run 7 fine.
As for your company, though - your hardware is archaic by today's standards. I'm sure it works fine for what you do, and that's fine to keep it. However, if you're going to spend time upgrading OSs, I would highly recommend you spend time upgrading your hardware, too, or else you won't see any kind of boost of anything at all. If you don't need to upgrade, why are you thinking about it?
If you find you want to be more productive or get a feature for new software, you're going to have to have the infrastructure to use it.