NVidia DSR downsampling coexisting with custom resolutions/refresh rates - I just got through doing a clean install of Windows 7 x64 and it took the afternoon for me to figure out how I was able to make this work before. So for posterity here are the steps:
1. Go to the NVidia Control Panel and turn off DSR by unchecking all DSR factors.
2. Define and test a custom resolution/refresh rate. Need to make sure that it won't crash the driver or harm the display
3. Start ToastyX's Custom Resolution Utility (link earlier in this thread)
4. Carefully follow ToastyX's quick start instructions
5. If you are using DSR then you are using an NVidia card - you must select "Custom Extension Block" from the drop down
6. Edit the custom extension block to include the custom resolution
7. When you are done, reboot or use the restart executable to cycle the graphics driver
8. Run the Custom Resolution Utility again to make sure changes are in effect - the display where you added a custom resolution should have two asterisks to indicate a modification and an extended block override
9. Go to the NVidia Control Panel - Display - Change Resolutions - for the display where you have a custom resolution - Click Customize
10. Check "Enable resolutions not exposed by the display"
11. An option that matches your custom resolution should now be available under the PC section - check the box next to that new resolution and it will now be an available standard resolution that you can switch to in the NVidia Control Panel. I use an extremely low custom resolution, and it does not appear in Windows Screen Resolution, only NVidia Control Panel.
12. Turn DSR back on.
With the custom resolution now exposed, it's now easy to create Display Changer II profiles for changing resolutions on the fly for whatever the game requires for top picture quality.