1. Start command prompt with administrator identity (start—all programs—accessories—command prompt—right click and choose to run by administrator), and type “diskpart.exe”, and press Enter.
2. After Diskpart runs, it would turn to DISKPART prompt, type “rescan” command and press Enter, it would scan hard drive configuration.
3. Type “list disk” and press Enter, disk list would be displayed.
4. Type “select disk volume” (such as “select disk 0”) and press Enter, then the drive where the hidden partition is would be chosen.
5. Type “list partition” command, and press Enter. Selected disk partition would be displayed.
6.  Type “select partition volume (such as select partition 2) ” and press Enter, then to choose the hidden partition.
7. Type “delete partition override”
Open Vista disk management, allocate volume number for the partition and format it, and then it could be used or united into other partition.
The operation is not that difficult, however, still suggest guys who should have experience of DOS command operation.