The link for the image shows the actual harddisk space vs the harddisk space in TreesizeIt all happened after I deleted a virtual machine from virtualbox, and noticed the space on my hard disk didn't free up. I checked the directory where the virtual machine image is stored, that was empty too. I have tried restarting the system, system restore, dskmgmt.msc, etc. But haven't been able to get back those 4Gbs I am missing in Treesize. Any suggestions?
Edit: I found the reason, Treesize is not showing the actual overall size of the drive but the size of files I have in those drives.
