Partial clone of virtual machine in VMware

http://www.vmware.com/pdf/vmware-tools-cli.pdf Page 13 :

Shrinking disks is not allowed under the following circumstances:

The virtual machine is hosted on an ESX/ESXi server. ESX/ESXi Server can shrink the size of a virtual disk only when a virtual machine is exported. The space occupied by the virtual disk on the ESX/ESXi server, however, does not change.

Because you are working with a spanned volume, you need to import all of the disks in one operation in order for the volume(s) to be correctly identified by Windows. If you try importing the disks one-by-one, as you have been doing, Windows will not correctly identify the volume(s) and will only give you the option to delete the existing data on the disk.

Helpful tip: since you are working in a virtual environment, it would not hurt to make copies of your vmdk's PRIOR to reattaching them just to be on the safe side. You can do this in vSphere client using the Datastore Browser.