With newer computers, or upgraded older computers getting a speed increase from SSD drives, you might not have enough space on that new drive to hold on the files stored on your DropBox cloud drive. To avoid running out of space, you may choose which folders to sync with your local computer. The following outlines the process:

Left click Dropbox icon in the system tray (lower right hand corner)
Left Click the Gear icon (upper right area)
Left Click Preferences
Left Click Account icon
Left Click Selective Sync
Uncheck boxes for folders that shouldn’t sync to your computer
Left Click Update
Left Click Ok