Flash drive space lost

I have just got a 16GB PNY flash drive 2 days ago so i could attempt to create a boot drive on it. I doubted i had set it up right so i wanted to start over. I formatted the drive, and now half of the space is missing. I am using Windows 7 so i tried using the Disk Management tool to try to find out what happened. In Disk Management I saw that the missing space still exists as unallocated space. I then tried to delete the partition so i could re-allocate all the space as one partition, but the delete option was grayed out. so now i have no idea how to get my space back.

So my question is how can I get my flash drive back to having 16gb of space on it?
 
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