Arun, problem solved! It was not, in face, a Parallels issue. I run PD on a laptop running Time Machine. At the time I installed PD and created a VM, i was not connected to my external drive for TM. So, after creating the VM, TM created a LOCAL backup on the laptop. Then after upgrading the O/S from Win 8.1 to 10, I renamed the VM from Win8.1 to Win10. Then TM made another LOCAL backup, including the "new" one which had a different filename, right! Then I decided to move the location to my OneDrive. See the problem? It wasn't until today that the old LOCAL backups got deleted and (see it coming...) my disk space has dropped back down to 170GB free! This would not have happened if I had turned off LOCAL TM backups in the first place till I settled down. Maybe the description of this issue can be simplified and turned into a FAQ for others. Thanks.