After buying a new computer a certain issue will arise where you will need to transfer all your data from one computer to the next.

Your Documents, pictures, emails, music, bookmarks, programs and settings will have to be migrated to your new computer. 

A change of hard drive will also require a data move.  Cloning software is also an option here where your hard drive will be copied bit for bit to your new drive and the end result is the exact same system except for the amount of additional storage space your new drive will have.