Problem in creating a partition at the disk

I have installed Windows 7 Ultimate on my Lenovo Z460 machine. The total disk space on the laptop is of 500GB. I partitioned the disk and I got 2 primary partitions and 2 logical drives plus an unallocated space of 104GB. I want to create a new partition with this unallocated space, but I am unable to do it, as this message appears:
“Cannot create a new partition, the disk already contain maximum number of partitions”
Would anyone please help me with some advice?
Thank you in advance!
