Windows 7 Hotkeys or keyboard shortcuts

Keyboard shortcuts are very useful for performing various task when you work on your computer, basically Keyboard shortcuts are the combination of two or more keys. They can make it easier to interact with your computer with saving your time.
following list is for some useful keyboard shortcuts:

Using General keyboard shortcuts :

F1 : Display Help
Ctrl + C (or Ctrl+Insert) : Copy the selected item
Ctrl + X : Cut the selected item
Ctrl + V (or Shift+Insert) : Paste the selected item
Ctrl + Z : Undo an action
Ctrl + Y : Redo an action
Delete (or Ctrl + D) : Delete the selected item and move it to the Recycle Bin
Shift + Delete : Delete the selected item without moving it to the Recycle Bin first
F2 : Rename the selected item
Ctrl + A : Select all items in a document or window
F3 : Search for a file or folder
Alt + Enter : Display properties for the selected item
Alt + F4 : Close the active item, or exit the active program
Ctrl + F4 : Close the active document (in programs that allow you to have multiple documents open simultaneously)
Alt + Tab : Switch between open items
Ctrl + Alt + Tab : Use the arrow keys to switch between open items
Ctrl + Mouse scroll wheel : Change the size of icons on the desktop
Ctrl + Esc : Open the Start menu
F5 (or Ctrl + R) : Refresh the active window
Esc : Cancel the current task
Ctrl + Shift + Esc : Open Task Manager

Using Windows logo keys:

Windows logo key : Open or close the Start menu.
Windows logo key + Pause : Display the System Properties dialog box.
Windows logo key + D : Display the desktop.
Windows logo key + M : Minimize all windows.
Windows logo key + Shift+M : Restore minimized windows to the desktop.
Windows logo key + E : Open Computer.
Windows logo key + F : Search for a file or folder.
Ctrl+Windows logo key + F : Search for computers (if you’re on a network).
Windows logo key + L : Lock your computer or switch users.
Windows logo key + R : Open the Run dialog box.
Windows logo key + T : Cycle through programs on the taskbar.
Windows logo key + Tab :Cycle through programs on the taskbar by using Aero Flip 3-D.
Windows logo key + Spacebar : Preview the desktop.
Windows logo key + Up Arrow : Maximize the window.
Windows logo key + Left Arrow : Maximize the window to the left side of the screen.
Windows logo key + Right Arrow : Maximize the window to the right side of the screen.
Windows logo key + Down Arrow : Minimize the window.
Windows logo key + Home : Minimize all but the active window.
Windows logo key + P : Choose a presentation display mode.
Windows logo key + G : Cycle through gadgets.