The hard drive format has begun!
You can check the progress by watching the Formatting: xx% indicator under the Status column in the top part of Disk Management or in the graphical representation of your hard drive in the bottom section.
If you chose a quick format, your hard drive should only take several seconds to format. If you chose the standard format, which I suggested, the time it takes the drive to format will depend almost completely on the size of the drive. A small drive will take a small amount of time to format and a very large drive will take a very long time to format.
Your hard drive's speed, as well as your overall computer's speed, play some part but the size is the biggest variable.
In the next step we'll look at whether the format completed as planned.