How t make 4 partitions

hi experts
i am rohan. i am using 250gb hard disk in my notebook. i am using vista home premimum. i am not able to make 4 partitions. i am only able to make 3 partitions of 112(c drive),55,55.
when i shrink c drive it says that u already have maximum no. no drives. but early my notebook had 4 parttions.

please help.

thanks