I have a small HDD - total volume 20 GB.
It is split in two - one partition is 15 GB and the other is 5 GB.

The small partition shows that there are only 490 MB free space on it while in reality the total volume of all the files that reside on it is 3,36 GB. So, 5 GB minus 3,36 GB = 1.64 GB free space, right?
Then why is it reporting that there are only 490 MBs of free space?
I don't have any hidden or system files on this drive that might be causing this.

What could be the reason for this and how to fix it?

There are two possible reason for the apparent anomaly. The size of the file doesn't necessarily reflect the space allocated on the disk due to what is know as slack space.

Space is allocated for files in clusters. If you are using NTFS each cluster will be 4kBs. If you are using FAT32 it will be 8Kbs. So each file will take up multiples of the cluster size.

So if you are formatted to FAT32 and save a file of 4 kbs in size it will take up 8kbs on the disk. A 9kb file will take up 16kbs of disk space.

Then there is the recycle bin. Have you looked in there. When a file is deleted it is still on the disk until it is cleared from the recycle bin.

Stuart

I have my Recycle bin disabled.
Actually this is the first optimization that I do to a freshly installed Windows. Never use the damn thing.

Anyways, I don't think that it is the file system that is causing the trouble here either.
I have never had a problem like that with this drive.
I've had it filled ot the max - almost 5 Gigs and now it reports that is almost filled at 3,36 Gigs.
Pretty strange.

Consider using the freeware pie utility suggested in Post 4 in this thread

http://computing.net/windowsxp/wwwb...

It will give you a graphic representation of all major files and folders from all directory levels at once.

i_Xp/VistaUser

To say it another way from StuartS ----

In Windows XPs NTFS file system, one Sector on the harddrive
amounts to 4,000 bytes. If a file is 1,000 bytes in size,
then that file will take up a full Sector, and you will lose
3,000 bytes of space. TWO FILES CANNOT OCCUPY THE SAME SECTOR.

If a file is 40,001 bytes in size, the it will use 11 Sectors,
and you will lose 3,999 bytes of space.

Right click on a file,
then click Properties,
then look on the General tab,
you will see two pieces of information, "File size", and "Size on Disk".
"File Size" might be 100 bytes, and yet
"Size on Disk" would be 4,000 bytes.

I find LOG files in Windows that show
0 bytes of File Size,
4,000 bytes of Size on Disk.

See my TWO Replies that I gave here ---
http://www.computing.net/windowsxp/...
to get back some space.

Hi StuartS,

Cluster size can vary. With FAT, up to at least 32K.

=====================================
If at first you don't succeed, you're about average.

M2

So it can, but as the OP was using a 5Gb drive his cluster size will be 8kbs. The bigger the drive, the bigger the cluster size.

Stuart

http://support.microsoft.com/defaul...
Overview of FAT, HPFS, and NTFS File Systems

The sectoer size is almost always 512. The CLUSTER size is settable in NT5.

To OP,

Try chkdsk; you may have hidden files you've overlooked.

=====================================
If at first you don't succeed, you're about average.

M2

Cluster sizes

for FAT32 are as follows:
512MB to 8,191MB = 4KB
8,192MB to 16,383MB = 8KB
16,384MB to 32,767MB = 16KB
Larger than 32,768MB = 32KB

NTFS - All partitions on a PC = 4KB default

Windows swap file will allocate drive space too.

>> The sectoer size is almost always 512 <<

I would go as far to say that the sector size is always 512 bytes. I have never seen anything else on a PC.

The sector size is determined by the hardware and is set by the manufacturer during the low level format as is the number of tracks.

The formatting process determines how many sectors there are to a cluster.

Stuart

Problem - solved.