No, once a disk is partitioned/formatted it cannot be downsized in the VMware Fusion UI however you can either make the virtual partition smaller from within the running OS, where supported, or use a third party tool like GParted Live. This will then only allow the virtual disk to only grow to the size of the virtual partition not the size of the virtual disk. This of course assumes the disk was not pre-allocated. Or you can use third party tools/utilities to image the contents of the existing virtual hard disk to a smaller right-sized virtual hard disk and then swap out the larger virtual hard disk for the smaller virtual hard disk. Symantec Norton Ghost is an example of a utility that can image disks.
