Ubuntu – How to create a new logical partition from unallocated space

Yes, you can easily add the unallocated space to the extended partition with GParted. Just select the extended partition (not one of the logical partitions inside it) and then choose the resize action.

You can not create a new primary partition from it; max. 4 primary or 3 primary + 1 extended partitions are allowed in the old MS-DOS (also incorrectly known as "MBR") partitioning scheme. So this has nothing to do with Windows OEM installations or whatever.

Uwe Plonus's explanation is correct, but gives no solution to your problem. Here's the solution:

1. Boot a Linux emergency disc. (The Ubuntu installer in its "try before installing" mode should work fine; or you can use Parted Magic or something similar.
2. Launch GParted.
3. If any of the logical partitions (those with numbers of 5 and up) are locked (typically with a little key icon, as in your screen shot), unmount them. There should be an option to do this when you right-click the icon. Your swap partition is the only one that's likely to be so affected, and its unmount opiton is called "swapoff."
4. Right-click the extended partition (this is easier in the list in the bottom pane of the window) and select the option to resize the partition.
5. Adjust the size of the extended partition to fill the available space.
6. Create your new partition within the extended partition, which should now contain the unallocated space.
7. Click the "apply" icon (typically a green check-mark).