vdisk manager is stored in /Library/Application Support/VMware Fusion/ It's a terminal application so if you open up terminal and drag it into there and hit enter you'll be given the individual options. It's an advanced way of modifying your virtual machine. In your case it would convert the virtual disk into the format you specify. It actually creates another virtual machine with the same information inside so once complete you'd have two. The difficulty with that is that you'll have to have enough space left on your computer to make the new one. So for example in terminal if I input the following command it should create a new virtual machine with the same information but a monolithic disk instead of split into 2GB chunks. "/Library/Application Support/vmware-vdiskmanager -r /Users/username/Documents/Virtual\ Machines/Windows\ XP\ Professional/Windows\ XP\ Professional.vmdk -t 0 /Users/username/Documents/Virtual\ Machines/XP_Pro.vmdk"

That should create a single growable virtual disk inside your Virtual Machines folder. From there you can create a new virtual machine using an existing virtual disk and choose that disk.

The other way of doing that sort of thing would be to use vCenter Converter to create a new virtual machine from the disks.

Normally if you have a snapshot and enter the Hard Disks section all options will be greyed out and there will be a notification that says "These settings cannot be changed while the virtual machine has a snapshot. To make these changes, first delete all snapshots."

If you open up your .vmwarevm there will probably be snapshot files there that the virtual machine depends upon. Fusion can sometimes loose the record of the snapshots during an upgrade to a higher version of fusion if the virtual machine has snapshots.