Problem: Unable to use a partition, even after formatting it and freeing it in windows.
It might happen some times that some partitions get marked as "unusable" Even after you format the partition and delete it from your windows partition manager.
One of the possible reasons for this is that you have more 4 Primary partitions in your system, i.e. you have created 4 partitions in your windows machine and all of them are primary partitions.
The only solution in such a case is delete one of the primary partitions, and then recreate the partition as extended or merge it with the unusable partition and create a new bigger partition.
If you are looking for a tool to manipulate the partitions check out
The GUI is pretty user friendly and easy to use.
NOTE: Before you do any thing with your partitions please take a back up of your system.