I have windows 7 and xp installed via paralells desktop on my mac mini. they are on the minis 256gb hard drive, and I am trying not to take up space on the drive as it is gwtting tight. so I have opted for automatically compress virtual machine in paralells configuration. but even with this setting checked, I did a compress virtual machine and then checked my hard drive space, and it went from 109gb free to 130gb free space on the 256 minis ssd. do I need to compress my virtual machines? and how often? and why doesnt the auto compression setting in paralells configuration for each virtual machine save this much space? would it be better to do a compress from the paralells options in the mac menu bar?