I know, the hard coded font stuff pisses me off to no end.
I need win7 for my music production software, it needs a lot of RAM and WinXP's magnifier isn't full screen, doesn't use acceleration so it's a pretty rubbish magnifier for me personally. I really wish I could do what I do, apart from work, in Linux (gaming, music prod) because then I could use KDE/Gnome which is a lot better with themes, and Compiz's magnifier is really nice.
Oddly enough, Windows 8 has much better theme control, although it's bloody ugly. If you use the 'classic' dark theme, you can still benefit from the full screen magnifier and a lot of the UI elements behave better in terms of using correct user chosen colors.. I'm just not terribly fond of Win8's metro thing and some other stuff irritates me. But I'll give it a bash once the final version is out and see how much I can gain from it, accessibility wise.
If you don't mind me asking, were your eyes that bad from birth? It's very rare I find someone with eyesight as bad/worse than mine, it's quite comforting to know there are others out there, and are also geeks