This is the question which pops in my mind that why not more than that 4 partitions

here is the info how many partitions we can create

actually in basic hard disk, we can create 4 partition(either primary or extended)

we can create maximum 4 primary
or 3 primary + 1 extended
or 2 primary + 1 extended
or 1 primary + 1 extended
not more then that? why and what is the reason?
The reason is because of a limitation of the MBR(Master Boot Record- the first sector of the harddisk.)
The MBR is only 512bytes of size, it is needed to store the primary boot loader, and the partition table. Typically, the area reserved for partition table is only 64 bytes. And the partition table entry for one partition is 16 bytes. So, 16×4=64. The space is over. so we cant create more than this

here are the sources for your reference

http://kbase.redhat.com/faq/docs/DOC-1653
http://en.wikipedia.org/wiki/Master_boot_record