vmware-vdiskmanager.exe Syntax

Hello,

I use the vmware Server 2 and I try to expand an diskvolume. The Syntax should be: vmware-vdiskmanager.exe -x 36GB myDisk.vmdk

I tryed vmware-vdiskmanager.exe -x 100Gb w2k8.vmdk and get the error: Failed to open the disk 'w2k8.vmdk' : A file was not found (0x1900000004).

I think I have to use the Datastorename but when I try vmware-vdiskmanager.exe -x 100Gb [standard]\w2k8-EMC\w2k8.vmdk i get the error: Failed to open the disk '[standard]\w2k8-EMC\w2k8.vmdk' : A file was not found (0x3000900000004)

Does anybody know the correct syntax?