How Can Windows DPI Settings

I want to use my laptop with Vista x64 as both "HTPC" and as a Work computer. Problem: When using it as a HTPC i need to change the DPI scaling in order to be able to read any text on the 27" screen. This is perfectly fine, but when using it as a Work computer this DPI setting wont look nice on the 15" inch screen. So I have to change it and restart the computer, a very awkward process in the long run. One idea i had was to create two users with one used for the HTPC since the DPI setting is global (HKLM) together with screen resolution and other hardware settings (like sound output). I basically just changed the Font size, Icon size and Border sizes for the HTPC user. This works sort of but, unfortunately, only seems to be valid for the Desktop and a select few menus in Vista (like the start menu, main control paned window) most sub windows and dialog boxes are still displayed with the puny 9 pts font

Another wild idea might be to run a "DPI Change-script" at startup, if it's even possible to change the DPI that way. Has anyone tried anything similar? I suppose it needs a restart anyway, but at least it would be automatic. Is there a registry tweak to make the font change apply to everything in Vista. or, a tweak to make the DPI setting Local? (i.e only aplies to current user) I guess, if it would be possible to make Windows apply these (DPI) changes without needing a restart, that would be acceptable.