Open Windows Explorer > "Organize" > "Folder and search options" > View tab.
In the Advanced Settings section, search for the "Use check boxes to select items" and check the corresponding box.
As from now you don't have to use the CTRL key to select multiple item, simply hover the mouse cursor over a file and a check box shall be available for multiple select!
From now on, when you hover your mouse over a file in Windows Explorer, a check box will appear next to it; click it to select the file. Once a file is selected, the checked box remains next to it; if you uncheck it, the box will disappear when you move your mouse away.