As you can see my Windows 7 dialog fonts are not anti-aliased, but other fonts are ok. How can I get the anti-aliased fonts back?
Make sure both ClearType and smooth edges on fonts (anti-aliasing) are on. Microsoft makes this super confusing by putting the two settings if two very different and hard-to-find places. But Start Menu search rules the world and if you know what to search for...!
For ClearType go to the Start Menu and type "Adjust ClearType text": enable "Turn on ClearType". Or from Control Panel > Appearance and Personalization > Adjust ClearType text > enable "Turn on CrearType".
For smooth edges go to the Start Menu and type "Adjust the appearance and performance of Windows" or from Computer > System Properties > Windows Experience Index (link) > [shield] Adjust visual effects (left sidebar) > enable "Smooth edges of screen fonts" (4th from bottom).