"Newegg has listed prices for OEM copies of Windows 7—technically intended for little computer building businesses, but there's nothing stopping you buying them. And as long as you understand some mostly-minor limitations, you can save some serious money."
This is a good way to get your hands on a copy of Windows 7. As long as you don't need to call someone like Dell or HP for support.
I am using Windows 7 as my main computer these days, and I love it.