Keyboard shortcuts are preset in the system, but you can add new ones or change them easily. For instance, change the default shortcut Ctrl+Alt+T (Run a Terminal) to Win+R (press R while holding down the Windows key, also known as Super key) by the following steps:
Go To System > Preferences > Keyboard Shortcuts

1. Browse to Desktop > "Run a terminal"
2. Click on the Shortcut, and it shows "New shortcut..."
3. Press Win+R, and it shows Mod4+R
4. Click the Close button and try the new shortcut.

•    To disable a shortcut, press Backspace when it shows "New shortcut..." after the step 3 above.

•    Shortcuts begin with XF86 refer to special keys available to some multimedia keyboards.

•    Keyboard shortcuts can also be set by changing keybinding values with Configuration Editor. Press Alt+F2 and enter gconf-editor, then navigate to apps > gnome_settings_daemon > keybindings, or apps > metacity > global_keybindings and window_keybindings.

Keyboard shortcuts can make using your PC a heck of a lot quicker. Listed below are some of the essentials - note that a plus symbol (+) indicates striking keys simultaneously.

Universal shortcuts
	Opens Start menu. You can also use CTRL + ESC
+ R	Open Run dialog
+ E	Open Windows Explorer
+ D	Show desktop
+ L	Lock computer
+ PAUSE or BREAK	Load system properties
+ B	Make the system tray active. Use Enter to simulate a double click, or use the arrow keys to select the icons
+ TAB	Windows XP: Cycle forward through applications in the taskbar Windows Vista: Cycle forward through Flip 3D + T cycles the taskbar forward in Vista
+ SHIFT + TAB	Windows XP: Cycle backward through applications in the taskbar Windows Vista: Cycle backward through Flip 3D + SHIFT + T cycles the taskbar backward in Vista
ALT + TAB	Cycle forward in task switcher
ALT + SHIFT + TAB	Cycle backward in task switcher
CTRL + ALT + DEL	Bring up the Windows Security dialog, allowing you to log out, change password, lock the computer, shutdown or run the Task Manager
CTRL + SHIFT + ESC	Load the Task Manager
PrintScreen	Take a screenshot, and copy it to the clipboard. To retrieve it, you'll need to paste it into an imaging program like Paint and save it

Windows Vista Only
+ any number	Hotkeys for the appropriate entry in the QuickLaunch bar. For example, + 1 will execute the first shortcut, + 2 the second, and so on.

File operations in Windows Explorer
CTRL + C	Copy the file
CTRL + X	Cut the file
CTRL + V	Paste the file. If you previously performed the copy shortcut, the file will be copied to the chosen location. If you previously performed the cut shortcut, the file will be moved to the chosen location
CTRL + Z	Undo the previous file operation
Holding CTRL when click dragging a file	Upon release of mouse button, force the file to copy to the new location
Holding ALT when click dragging a file	Upon release of mouse button, create a shortcut to the file in the new location
Holding SHIFT when click dragging a file	Upon release of mouse button, force the file to move to the new location
ALT + ENTER or ALT + double left click on icons	Load the properties dialog
SHIFT + DEL	Delete file immediately, without sending it to the Recycle Bin.
SHIFT + arrow keys, or HOME/END	Group select/deselect multiple sequential files
CTRL + left click	Select/deselect multiple specific files
F2	Rename file
F3	Open search Explorer bar
F4	Go to address bar
F5	Refresh contents
Numpad *	Expand entire selected folder tree
CTRL+ A	Select all files in current window
or numpad +	Expand current folder
or numpad -	Collapse current folder
BACKSPACE	Go up to parent folder

Shortcuts with text
CTRL + or	Place the cursor at the beginning or the end of the current word.
CTRL + END	Send the cursor to the end of the document
CTRL + HOME	Send the cursor to the beginning of the document
Double click	Quick select the clicked word
Triple click	Quick select the clicked paragraph
SHIFT + arrows, HOME, END, PAGE UP or PAGE DOWN	Select text

Navigation without a mouse
SHIFT + F10	Same as right clicking a file
TAB	Navigate menu elements forward
SHIFT + TAB	Navigate menu elements backward
ALT + F4	Close the current application
ALT + SPACEBAR	Display application system menu
ALT + Underlined letter in menu	Open that menu
SPACEBAR	If a checkbox or radio box is selected, activates this. If a button is selected, clicks it
ENTER	Click the default button (usually OK)
ESC	Equivalent to clicking the CANCEL button