You can also run Disk Defragment through My Computer - Right Click on the
drive you want to Defrag - choose Properties - click Tools tab - click
Defragment.
But you must know that where is your defragment command is located in your
computer. As mentioned by STEAM the path is %SystemRoot%\System32\dfrg.msc.
You also run Defrag by typing or browsing this command in START - RUN.
To create a shortcut on Desktop. Right-click on Desktop - point to New -
Shortcut - type the above path (or make a copy - paste) and finish the wizard.
To create a shortcut back in System Tools - Right click on Start Menu -
click Open / Explorer - Goto System Tools under Programs - Accessories then
right-click New - Shortcut (same as above).
In future, if you want to avoid asking these kind of question then you must
know that about your favorite or most used program locations. To know about
any of your program location, right-click on any program shortcut like
Notepad and choose Properties - click the Shortcut Tab - here you can see the
path in Target window.
Let us know, if this information is useful to you.