The amount of disk space used, as shown in Disk Properties, and the total file sizes, as shown by JDiskReport, should not agree -- these are reporting two completely different things. If you examine the JDiskReport, you will find no reference whatsoever to the amount of disk space actually used; similarly, Disk Properties makes no reference to file sizes.
Two factors come into play here. First, because files must be stored in an integer number of clusters, they always use more space than their actual size (unless the file just happens to be an exact multiple of the cluster size). For disks greater than 2 GB, NTFS uses 4096 bit clusters; thus a 1 byte file would use 4096 bytes of disk space, as would a 4096 byte file. This also applies to the last cluster af a large file. On the average, therefore, each file uses 2 kilobytes more disk space than the actual file size. If your laptop has about 70,000 files, quite typical, excess disk usage by files (called slack) would be about 140 MB.
Second, and more significant, is the fact that NTFS itself uses disk space to keep track of the files and their locations. NTFS reserves 12% of the disk space, 4 GB in your case, for its MFT (master file table). Not all of this is reported as used by Disk Properties; it includes any free space in the MFT in its report of free space. The bottom line is that for a system such as your laptop, you should normally expect between 3 and 4 GB difference between total file sizes as reported by JDiskReport, and disk use as reported by Disk Properties. That is indeed the difference on my laptop of size similar to yours.
You report about 10 GB difference -- and I find that hard to explain. The fact that three third-party utilities agree on file sizes makes me think that a check using the DOS dir command would also give the same answer. Could you have some software that "really hides" files -- not just setting an attribute bit thet JDiskReport reads and includes in the total? Some malware, I am told, hides itself very effectively and may not be counted.
On the other hand, could the disk usage reported by Disk Properties be wrong? You got the usage figure by subtracting free space from total capaciity. But Disk Properties reports usage also; were the three consistant, with the sum of use and free equal to the capacity plus or minus 0.1? Were the reported bytes consistant with the reported GB? (Divide the bytes by 1.07374 to get binary GB.)
Sorry I can't be more help at this time regarding the exceptionally large discrepancy. Please let us know if you find the cause or come up with additional information.
Frank
I run XP on a 40GB drive on IBM Laptop. Disk management shows two partitions -FAT 3.9GB labelled 'IBM Service' and NTFS 33.3GB labelled C: and when I look at 'My Computer', C: lists as 33.3 GB with 6.2GB available. So far, so good. That would indicate about 27 of my 33 GB are used.
But various 3rd party disk analysis tools keep showing total used disk at 17GB. For example: JDiskReport, DiskSpacePlus and SequioaView. Why the discrepency - am I really missing 10GB somewhere? Chkdsk /f hasn't found anything.
Suggestions, pls?
Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic