BleepingComputer.com: problems during disk partition in disk management

i have a C: drive containing operating system,having memory 220.27GB.148.82 GB of this memory is free(not in use).
i tried for partition of my disk.i entersd as an administrater.then i go to the computer management where i click on the disk management.
there i found disk 0 containing four partitions :
(1)118MB healthy(EISA configuration)
(2)RECOVERY (D:) 10.00GB NTFS Healthy(primary partition)
(3)OS (C:) 220.27GB NTFS Healthy(system,boot,active,primary partition)
(4)2.50GB Healthy (primary partition)
now i right click on the OS(C:) and choose shrink volume.it shows available size of shrink space 37807 in MB.now i enter 25600 amount of space to shrink in MB.
now it shows a unallocated partition of 25 GB space.
now i right click on this unallocated partition and click on the New Simple Volume..now a new simple volume wizard is opened..i click on the next..then using the maximum simple volume 25599 MB again click on the next.now by assigning the drive letter again click on the next.now i choose FORMATE THIS VOLUME with settings as:
1. file system NTFS
2. allocation unit size DEFAULT
3. volume lable NEW
and then i click on the next..finally i click on finish for completing the new simple volume wizard.
THEN A ERROR MESSAGE WAS DISPLAYED:
you can not create a new volume in this allocated space because the disk already contain the maximum number of partitions.


what should i have to do to create further partitions...can i delete existing partitions.if yes then which partition can be deleted safely without harming the system...please solve this problem...