3.5.4.4 Querying Disk Partitions
Prior to any method that references a partition (CprepDiskWriteFileData, CprepDiskVerifyFileData, CprepDiskDeleteFile, CprepDiskDiskPartitionIsNtfs, and CprepDiskGetFSName), a client MUST call CprepDiskOnline to transition the ClusPrepDisk.OnlineState to Online. In subsequent methods that reference a partition, the client SHOULD NOT designate a partition number outside the integer range of 1 to the number of partitions returned by CprepDiskOnline.