Extended partition new size not shown in My Computer Windows Server 2003 SP2

Dell Power Edge2900 Server

Windows 2003 32bit, SP2
Dell PERC5/i Raid Controller.

1.      2X146GB (System volume, Drive C) Disk0 - RAID 1
2.      4X300GB (For Data , Drive D) Disk1 - RAID 5

We added new 4x300GB HDD and extend the Disk1 and through “diskpart” we expand the “D” partition from 850GB to 1950GB successfully but in “My Computer” still showing 850GB insist 1.95TB.

I’ll highly appreciate your kind support in this subject.