I have a Windows XP x64 install in VMware Fusion. The amount of space that the VM reports as used (C:) is ~20GB. However, the amount of space the VM is taking up on my disk is 30GB. Why the inconsistency? I do not have autoprotect enabled, nor do I have any snapshots I'm aware of. I have defragmented the drive and used Drive Cleanup from the VMware settings.
If you've suspended the VM then it'll have some space allocated for memory on disk too. I'm guessing you don't have 10GB RAM allocated to the virtual machine, but it might account for some of the extra space.