No one has correctly answered Matthew's question. Myself, like him, do not care about cleaning up the space inside the Windows VM. We want to know when we are using the Mac parallels software, why we cannot make the harddrive space smaller using the mac parallels gui. We both started with 128 GB, We both see messages in windows saying 70GB + is free, or unused, we both can do simple math to figure out that a new setting of 80GB will still leave plenty of room in windows. We both tried setting the new size to 80 GB, both clicked apply, and we both received the same result. Parallels "gives up" or "aborts" the action without any message informing us why. I'm already anticipating some circle talking not useful reply, and if that's coming, then please parallels, tell me why your gui allows for an unactionable action to happen without any message informing us on why it didn't commit the request.