[Irish]

Running windows XP ive found a curious discrepancy, when looking at the properties of my c drive it says 32gb of my hard drive is in use, however when I select all the files and folders they only come to about 27gb. Any suggestions on where the other 5 gig is gone?

Any help is appreciated....

[Osiris]

Size refers to the files actual byte count. Size on disk refers to the amount of cluster allocation the file is taking up.

Drives are organized by fixed-size units called clusters. The size of a cluster depends on several factors, the most crucial being file system and partition size.

Some background to help you understand:
Back in the days of DOS and Win95, the only usuable file system was FAT16 (also known as FAT). Because hard drives were so small back then (1GB was considered HUGE), FAT's limitations were minor, one of which was the limitation that the maximum partition size was 2GB.
With FAT16, the cluster size within a partition was determined by the size of the partition. Here is a chart showing the default cluster size for various FAT16 partition sizes:

Code:
Drive Size FAT Type Sectors Cluster (logical volume) Per Cluster Size ----------------- -------- ----------- ------- 0 MB - 15 MB 12-bit 8 4K 16 MB - 127 MB 16-bit 4 2K 128 MB - 255 MB 16-bit 8 4K 256 MB - 511 MB 16-bit 16 8K 512 MB - 1023 MB 16-bit 32 16K 1024 MB - 2048 MB 16-bit 64 32K
Now, with small drives, this wasn't a problem because partitions were small. Once drives started growing, the cluster size issue became problematic.

Here's why:
When you write a file to disk, the smallest unit it can take up is 1 cluster. If you have a 1024MB (1GB) partition, and the default cluster size is 32KB, a 1KB file will take up a 16k cluster.
Since you can't have more than one file occupying a cluster, the remainder of that cluster is considered wasted space. In this example, a 1KB file is taking up 32KB of disk space, and wasting 31KB of that space.
Say you have a 68KB file. That file will be written acrosss several clusters, since a cluster is smaller than the actual file. Thus, a 68KB file will take up 2 full 32KB clusters, and 4KB of a third cluster, while also wasting 28KB of that third cluster. While the file is only 68KB, it's taking up 96KB of disk space.

As you can see, with a lot of small files, you can waste a ton of space on such a drive.

To remedy the situation, MS unveiled FAT32 with the introduction of Windows 98. FAT32 not only allowed for significantly larger partition sizes, but also reduced the default cluster size dramatically. Under FAT16, a 2GB partition used a default cluster size of 64KB. Under FAT32, that was reduced to 4KB. A 16GB partition only used 8KB clusters, and up to 32GB uses only 16KB clusters.
As you can see, the savings on such large drives can be significant, resulting in more usuable drive space.

With Windows XP, the home user was introduced to NTFS. Under NTFS, a 1GB partition uses 2KB clusters, and anything above that up to 2TB (terabytes) only uses 4KB clusters.

So, the reason you're seeing that difference is because when you select properties, the Space On Disk reading is accounting for the wasted space attributable to the cluster size on the disk.

File Size vs "size on disk" [Archive] - Alien Soup

Note: MS has a chart with the cluster sizes listed on TechNet.

[Mak213]

Pagefile, Hibernation, System Restore

[Lexluethar]

Wow, awesome explanation Osiris!

[Irish]

Thanks for the detailed reply, but im not sure that thats the problem, looking at the properties it lists size and size on disk with a discrepancy of about 100 megs.

When looking at properties of all selected files in c: and the actual properties of c: itself theses a discrepancy of about 5 gigs, this is a big discrepancy for NTFS even with a lot of small files.

Any other suggestions? (My system restore is only set to 2 gig, can anyone explain page file and hibernation to me? Thanks in advance...)

[Osiris]

Has the OS been installed from scratch by you or say from Dell, IBM, HP, Etc?

[Osiris]

Not my EXP, forgot to add the source

[Irish]

Installed it from scratch myself, I probably should have mentioned that i have three partitions of my hard drive, I have ubuntu linux installed aswell with a FAT 32 swap partition, would this affect anything?

But linux shouldnt have anything stored on my windows partition should it?

[Mak213]

Depending on how much RAM you have will determine if the pagefile, and hibernation are the reason for the rest of the space.

Hibernation will keep aside that amount of space for when your system goes into Standby/hibernation so it can store the data on the hard drive as yoru system "sleeps" as the data will be erased from RAM once it goes into sleep mode.

This is how they are able to use hibernation. Pagefile is just like RAM on your hard drive.