I converted a growable disk to preallocated one using following command:
E:\VMs\MD-WIN7-V4>"C:\Program Files (x86)\VMware\VMware Workstation\vmware-vdiskmanager.exe" -r "MD Windows 7 x64 V3-cl3.vmdk" -t 2 MD-WIN7-V4_E.vmdk
Creating disk 'MD-WIN7-V4_E.vmdk'
Convert: 100% done.
Virtual disk conversion successful.
As a result I see new vmdk file in same folder.
549,755,813,888 MD-WIN7-V4_E-flat.vmdk
I can still start the origial vm using old growable virtual disk ""MD Windows 7 x64 V3-cl3.vmdk". But I wanted to use new vmdk file, so I followed instruction in KB 2010196 (https://kb.vmware.com/s/article/2010196) and it failed with following error
"The file specified is not a virtual disk."
I'm using VMWare Workstation 12 RPO.