Different dpi per monitor windows 7?

I have Lenovo thinkpad 15.6″ display with resolution: 1920x1080 and an extended display: ThinkVision: 19″ display with resolution: 1440x900.
I need to set different dpi for both the monitors. Is this possible, if yes then how?

No, not in Windows 7, DPI settings affect the entire desktop, regardless of number or arrangement of monitors.

First possible since Windows 8.1 due to DPI scaling enhancements.

There is workaround that will allow you to do something very similar to per-monitor DPI if you have a recent Nvidia GPU and drivers (9XX or higher).

1. Right click on your Desktop
2. Open the Nvidia control panel
3. Go to 3D settings
4. In the global tab, find "DSR - factors"
5. Select all options
6. Click apply
7. Go to the resolution settings, and set your smaller screen resolution to a resolution similar to the bigger screen. Preferably choose 2x resolution to minimize the blur of DSR.

While it's not most elegant solution, it works and is better than turning down the resolution of another screen.

Troubleshooting:

Sometimes DSR will not accept your native resolution. If that's the case, then do the following:

• Download Custom Resolution Utility
• Launch it
• Select the offending (smaller) display
• Remove all resolutions that are bigger than native. Watch for "extra" reported resolutions hidden under "Extension blocks".
• Edit your extension block (NOT REMOVE), and look for data blocks that state "X resolutions". Edit them and purge everything bigger than native.
• After saving the changes (pressing OK, so program quits) use "restart" and "restart64" to restart your graphic driver and make it register changes.
• Be aware, your screen will go black for a second and may go small res, don't worry and let it work.
• After applying this workaround to the bad DSR native resolutions, uncheck all the DSR's applied, and check them again (so the DSR resolutions will be reloaded/recreated).

update for free to Windows 10 (till 29. July 2016) and here you also have the option to manually change the DPI per Monitor in the settings app.