Task Scheduler can be used to schedule commands, programs, or scripts to run at specific times. For example, if you want to regularly backup your data, you can schedule the program to run at the end of the day, when you are through with your work.
Windows lets you drag commands, programs, or script files into the Scheduled Tasks folder to automatically schedule a task. This registry setting disables the ability to drag-and-drop or copy & paste a program into Scheduled Task folder.
Alternatively, you can add a task through wizard. So, even after disabling the drag-and-drop functionality, there are means to schedule tasks.
For this, go to Start > Run menu, enter “regedit” and navigate to the registry path listed below. If any of the subkeys “\Windows\Task Scheduler5.0” does not exist, create it as explained below. Then, create a DWORD value “DragAndDrop” in the right panel.
Now, right-click and modify its value to "1" to enable drag and drop restriction. However, if you want to get back to the original state and disable restriction, change the value to "0".
The changes take effect after a restart or logoff.