In excel Cursor not converting..

[baren20]

From today i am not able to drag the cursor of excel from cell to cell. I can only select the cells but dragging option is not coming for sum or applied formula to all cells through pressing down right corner of single cell. 

 i have attached the picture to understand the area.

please help me..

[#2]

@baren20 

Select File > Options.

Select Advanced in the navigation pane on the left hand side.

Under 'Editing options', tick the check box 'Enable fill handle and cell drag-and-drop'.

Click OK.