Got an error while creating a partition using Acronis Disk Director

Hi Gurus,
I was using Acronis Disk Director to partition my hard disk so that I can have multiple OS which I require for my program testing.
However, I got this error message while creating another partition for a new OS (see screenshot below).

Error
Acronis Disk Director Suite was not able to create the partition because there is no enough free space on the selected hard disk drive.
I checked my available disk space, and it turned out that I had enough for another partition.
I need your expertise here, gurus.
Please help.
