Wait, what? Windows has got full custom DPI control and has had for years. Under Windows 7 there's a dialog box to set it under the Appearance & Personalisation / Display control panel. You can toggle XP scale mode for compatibility with older apps.

Seems rather more flexible than pixel-doubling - I thought that went out with underpowered games consoles, but apparently not.

Where there is an issue is with icon scaling - since these are just multi-resolution bitmaps, if the person who made them didn't include the larger sizes you're going to have an ugly time at non-standard DPI settings.