Hi all, I noticed this little problem the other day, and can't quite figure it out. When I check the size of my hard drive by selecting all the files and folder (including hidden and system files and folders) the size comes out to about 5 gigs. When I check the size of my hard drive by right clicking the drive and selecting properties, it reports almost 10 gigs used. This is a 30 gig hard drive. I'm just wondering if anyone knows how to account for this usage of space. Also, I have two hard drives, this is the only one that experiences this behavior. If anyone can help I'd greatly appreciate it. Thanks, Mike

Slack space is the answer, although 50% is quite a lot but would be possible if you have a 30MB disk formatted to FAT32 and a lot of relatively small files. It is to do with the way the operating system allocates space. When creating a file on a disk, space is allocated in clusters. The size of there clusters will vary depending on the size of the disk. If the cluster size is 16 MB which would be the case with a 30MB Fat 32 disk, then evey file will take up spce in multiples of 16 MBs. Even a small 1 KB file will use 16 MB of space. The unused space is know as slack space and can only ever be used by the file it is allocated to. The way round the problem is to use NTFS. It won't eliminate the problem altogether but will reduce it considerably. Alternatively split your 30 MB down to smaller partitions which will give you a smaller cluster sizes. However, if you are already using NTFS and are getting a mis-smatch between space used and space free remember to take into consideration the System Volume Information plus any Revovery files there may be hidden about. So it can be seen that simply adding up files and folder sizes is never going to give you an accurate idea of space used. The way the OS does it is to find how much space is allocated to a file, not necesserrily the same as home much space the file is using. Stuart

Stuart, Thanks for your helpful reply. The disk is already using NTFS. In fact, the other hard disk is also using NTFS, but I don't see the problem there. So you're basically saying that the properties window for the drive gives the accurate measurement? One more thing to add, this also seemed to happen suddenly, I never noticed this behavior before. Thanks again for your help. Mike

The Operating System knows about the hidden system files, temporary files and stuff that the user will be unaware of, so that that do the work. Have you checked the Temp folder? That can contain a fair amount, including sub folders. Stuart

Stuart, most of your explanation is correct with the exception of the cluster size. The cluster size would be 16k, not 16m. A 1k file is not going to use 16meg of drive space.