The Dell policy concerning the internal FSM (Factory Service Menu) is this; if you break the monitor by making some change in the FSM, the purchased warranty is voided.

OD (OverDrive) on works hand in hand with the uniformity compensation zonal color tuning. By turning OD off in the FSM, you are breaking the Menu OSD- Response Time option (8ms for Normal mode, 5ms for Fast mode). 

After OD is set back to on, try these steps in the user Menu OSD =
* Under Display set Uniformity Compensation to Off and retest
* Under Display set Response Time to Normal and retest
* Under Brightness/Contrast set Contrast to 50 or below and retest
* Under Brightness/Contrast set Contrast to 80 or above and retest
* After making the Contrast change above, any further Contrast adjustments should be made from within the GPU control panel

If the steps do not help, your only alternative is set OD to off and forego the usage of Response Time settings.

Thanks Chris. I have tried the options you gave, but the ghosting is still there. I don't need to remember "OD Gain" value (40 by default) because, it reset every time the monitor is on. Is there anyway I can save the "OD Gain"?

I am not aware of any way to do this.

Do you have any other method to solve the ghosting? So far, only setting the OD (OverDrive) feature to Off in the FSM seems to help . I am happy to try other solutions.

I have not seen any other method internally or out here.