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#1
Unallocated means its not formated and unformatted drives don't get a drive letter. Format it and windows will assign it a drive letter.
Amazing how you can do all that but yet not know how to format the unallocated space to make another partition.
As mentioned format it.
It may not let you as you already have 4 primary partitions.
Interesting reading here.
http://www.ahuka.com/other/partition.html
It reports all the other partitions have 100% free space. Nothing on them, yet?
If not, delete them. Expand the C partiton 150GB. then, recrete the other partitions.
You can only extend a partiton if Unallocated is next to it, so if nothing is on the other partitons now is the time to delete and re-size.
From the posted image, it looks like the first two partitions are for win 7, next three partitions are for Linux (Ubuntu and Fedora and Swap) and the unallocated space is the free space.
A hard disk allows only 4 primary partitions and as you have already used them up, you can creat an extended partition and one or more logical drives on the free space using Disk management tool of Windows 7.