One of the drives in my system is a WD VRap 150 GB, SATA which I dedicate to only run Flight Simulation. When first installed and formatted it showed 139 GB’s available. I have two files loaded on this drive: Flight Simulator X taking 62.3 GB’s of space. I also have flight Simulator Addons taking 4.63 KB. A total of 63 GB’s. When I subtract the 63 GB’s from the 139 GB’s I get 76 GB’s that should be available. However properties only show 36 GB’s available. That shows that there is 40 GB’s somewhere. Flight Simulator X runs best on a drive that has around 50% free space and I would prefer to run it that way. No one has been able to tell me what happened to the 40 GB’s as yet. My question is: I have these files backed up as image files on an external drive. Would it be safe to delete these files from the HDD, do a new format and then re-install the FSX files back on the HDD? Is there a chance that will restore the lost 40 GB’s? Am I liable to get into trouble here? Thanks for the help.