I got a Mac Mini at about summer in 2011 and I'm looking to use it along with my main PC using a Dell Ultrasharp U2412M monitor. The monitor's DVI is used by my main PC, so I picked up a Mini DisplayPort to VGA adapter (at the time I didn't actually know the monitor had a DisplayPort on it, but I'd still need a Mini DisplayPort -> DisplayPort adapter) and tried it.
But I can only set the Mac Mini's resolution to 1920x1080 in System Preferences.
I tried modifying my com.apple.Boot.plist file in Library/Preferences/SystemConfiguration, and it currently looks like this :
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
<key>Kernel Flags</key>
<string></string>
<key>Graphics Mode</key>
<string>1920x1200x32</string>
</dict>
</plist>
That doesn't seem to have helped. Any further ideas?