From Microsoft's Knowledge-base article #2544872 - The DPI adjustment is not available in a Remote Session (RDP):
When regular users connect to a remote session, they are unable to change the resolution of the display or the DPI settings. The DPI settings would normally be used to make a global change to the size of the fonts and other user-interface elements; for example to increase the UI legibility.
This is about Server 2008 R2, but the same effect is what you're running into with Windows 7.
They suggest a workaround where you create a upscaled theme and then copy it to the client computer(s):
In order to provide a simple solution to users, it is recommended that an Administrator create several Themes with different sized fonts and UI elements, named in a discoverable way (e.g. "120dpi Theme", "150dpi Theme"). This will enable remote desktop users to easily select a Theme with scaled-up user interface elements, from a familiar place in Windows (i.e. Personalization applet; also accessible via a right-click on the desktop)
Full information and instructions are available in the MS KB; Perhaps they'll work for you. :)
More information on the situation, and another possible work-around, can be found here.