Windows have troubles with partition ordering.
Your last partition is an extended one (thus it can contain several partitions).
A Windows disk can have:
- 0 to 4 primary partitions
- 0 to 1 extended partition (1 extended only if 0 to 3 primary)
- the extended partition can contain 0 to 63 partitions
They are 4 partitions slots into the boot sector.
The primary partitions have to be the first ones (this is a limitation for Microsoft products only). Then comes the extended partition.
Seems your Windows used slot 1 and 2 for your first partitions (both primary) and slot 3 to store your extended partition's informations. So slot 4 is empty. So you cant have another primary partition because its slot has to be before the extended on.
You can try with a live Linux CD. Most of then include a graphical partitionning utility. And I never had any issue with them.
With a little chance this utility will remap the slots correctly.
Else you have to use some command line tool. Read manual, etc.