Windows 7 does not really support high DPI settings very well at all. I think only 100/125/150% were properly supported, but even then, poorly.
I would really suggest upgrading to Windows 8.1 when using a high DPI display.
That aside, set Media Center's font size to 4pt.
Tools → Options → Tree & View → Select Font…
Now set Media Center's scale to 200%. View → Size → 200%
Restart Media Center.
There is a bug in Media Center where Windows' DPI settings are applied to the font size, but not the rest of the UI.
This means that since you have Windows set to 225% (200% is likely to scale better, for what it's worth) the original 9pt text at 100% size, is being rendered at 30pt (3.4x size) while the UI is at 1.5x size with your current settings.
With the settings above, it should be scaled to 18pt with 2x size text and a 2x scale UI, which should look a lot better.