Hi. I am in the process of cleaning up my C: drive as I move all data across to a 2TB NAS and I have the properties on my User drive showing 48Gb of data, yet there is virtually nothing in any of the remaining sub-folders. Has anyone experienced this and found an reason/solution to seeing 'invisible' data; deleting /moving it; and getting properties to tally with folder-by-folder view of used space?

There is a "Hidden" attribute for files and folders. You can set Windows Explorer to show you hidden files. Click Start, then type folder into the search box. When Folder Options comes up, click it, then go to the View tab. There you will find a couple of radio buttons that govern whether hidden files, folders or drives are shown. Also, your OS is typically on your C: drive. Is that 48 GB the total space used on C:? The OS does take a significant amount of storage. -Noel

Thanks Noel. My main concern is losing data, as I will be re-formatting the drive and donating the old PC to my sons' school. I have discovered a (previously hidden) folder called 'AppData' that is 47.7GB. So, that's the 48GB identified. The strange thing is that Properties at Root C: states 90GB used; 48GB + 16GB for Windows + 6.5GB for Program Files + 1.25Gb for Program Data + 8GB that Windows used when it assigned a second drive (D:) = 80GB. Where would the other 10GB be? I have scoured all folders off Root and there's nothing that adds up to 10GB. Strange.... Thanks again, Ed.

Have you emptied the Recycle Bin? Deleted files still take up space until you do that. -Noel

Would the Page and Hiber files on C: account for your difference?

I'd run chkdsk to get a summary of the disk usage. The 10gb could be NTFS system files. Example: chkdsk d: Summary provided by chkdsk (I’ve highlighted the NTFS system file usage): 488383487 KB total disk space. 34019148 KB in 788 files. 568 KB in 137 indexes. 0 KB in bad sectors. 86319 KB in use by the system. 65536 KB occupied by the log file. 454277452 KB available on disk.