Windows 7: Cannot do anything with unallocated space

I have a 3TB external drive that I've been using for backup and general storage, and decided to make a new partition on it to keep the two things separated better. Using Windows' Disk Management tool I tried to shrink the volume by 775GB, but ended up with two new slots of unallocated space, one was about 28GB and the other is 746GB. I was able to create a new volume using the 28GB, but deleted it since it wasn't enough and extended the primary partition using that space. HOWEVER, the larger block of unallocated space I can't seem to be able to do anything with. As you can see in the screens, everything is grey'd out.
Do I need to reformat the whole drive to be able to use this space again?

Hello mate, how does Partition Wizard see that space?

Partition Wizard Free Home Edition

There is nothing wrong with what you are seeing, it is just a limitation of the MBR which means that disks larger than 2TiB (2048GiB) are only recognised up to that size limit (anything over that is not recognised, even if it is just a couple of GiB or one or more TiB). This is because the partition pointers in the MBR cannot exceed the 2TiB limit.

It looks an awful lot like you are dealing with the legacy 2.2TB limitation in NTFS formatting. That should not be an issue since you are running Windows 7 64 bit, but perhaps it is coming up because of the external drive or an older enclosure.
Perhaps you need to utilize a driver/partitioning utility (from Paragon Software or Partition Wizard as Barefoot suggests) to use the entire drive.

See here for more info:
Everything You Need to Know About 3TB Hard Drives | PCWorld

EDIT: Yikes. It took me 6 minutes to write that? Sorry Dwarf!

I was able to use partition wizard to extend the drive to its full size. Thank you very much Bare Foot Kid

Good to see you found a solution.

Another happy customer!
Glad you got it sorted!

haha it took me about 15 minutes to download and install partition wizard then reply

also that's an interesting read TVeblen thanks for the reference. and thank you Dwarf and TVeblen for clarifying what i was seeing