As we know, hard disk is the main storage media for computers. However, after purchasing a new hard disk or using a disk for a period of time, we may find some hard drive space is missing without us knowing the exact reason. After a series of researches and tests, 6 possible causes are found, and next I will introduce these causes one by one, with showing corresponding ways to find the hidden hard drive space back in Windows OS.
1.Hard Disk Manufacturers Does not Give Capacity They Promise
On the market there are different capacities of hard disk, including 500GB, 1T, 2TB, and so on. However, when checking capacity of the newly bought hard disk in Windows Disk Management or by adding space of each drive, we may find the real disk size is always dozens of GB smaller than that manufacturers advertise. What’s the reason? Here, we take 500GB hard disk for example to show users the exact reason. The following thumbnail shows a 500GB hard disk’s real capacity is 465GB:
Next, let’s see how this result is figured out. For hard disk manufacturers 1 GB = 1000 MB, 1 MB = 1000 KB, and 1KB = 1000 B (byte), but actually 1 GB = 1024 MB, 1 MB = 1024 KB, and 1 KB = 1024 B. Therefore a 500 GB hard disk is just (500 * 1000 * 1000 * 1000) 500,000,000,000 B for manufacturers. Converted to GB, it is 5000,000,000,000/1024/1024/1024 ≈ 465GB. Similarly, a 1TB hard disk will be 931GB. This is the cause. Under this situation, we have nothing to do for the missing disk space.
2.Hidden Partitions Take up Space
After we install Windows OS on a never used hard disk, some hidden partitions may be created automatically, such as the system reserved partition, recovery partition, OEM partition, and EFI system partition. All these hidden partitions will not be shown in Windows explorer since they do not have a drive letter, but we can see them in Windows Disk Management:
Since these hidden partitions are of great significance (some are related to system recovery and some affect the boot of Windows), Windows hide them to avoid mistaken operation and virus attack, and users had better not delete them to release space. However, if there is no need to keep them any more (a system backup has been made, for example) but you cannot delete them in Disk Management, please see Cannot Delete Volumes in Windows to get solutions.
Under this situation, we know where the missing hard drive space is, but it saves files.
3.There Is Unpartitioned Hard Disk Space
A newly bought hard disk cannot be used to save data unless we partition it. To be specific, we need to create partitions on the disk. Only partitioned space can be visible in Windows Explorer (a partition without drive letter is invisible in Windows Explorer, too), but we can see unpartitioned space (also called unallocated space) in Disk Management. For example, there are 3 partitions and 2 unallocated spaces in my computer:
But I can see 3 partitions only in Windows Explorer:
To make use of unallocated space, we need to create partition(s) in it, which can be completed in Disk Management. Detailed steps: right click the unallocated space, choose “New Simple Volume”, set partition size, drive letter, file system, allocation unit size (cluster size), and volume label (optional) for the new partition, perform a quick format, and at last make all changes applied.
Of course, we can also extend an existing partition to the unallocated space. Since Windows Vista, the “Extend Volume” feature has been added to Windows snap-in Disk Management utility, but disappointingly it can only extend a partition to the right contiguous unallocated space. If the unallocated space is nonadjacent to the partition we want to enlarge or the partition is formatted with FAT, “Extend Volume” will be grayed out. But fortunately there is partitioning tool that can extend a partition by taking free space from any unallocated space on the same disk without users converting to dynamic disk, and MiniTool Partition Wizard (freeware) is a good choice. Please see Extend Partition to get detailed steps.
Under this situation, we can find out and reuse the hidden hard drive space.
4.System Protection Takes up Much Space
When checking properties of a certain partition (especially system partition), we may find its used space is 9.32GB or larger:
However, after opening this partition and viewing properties of all its files we may find the real file size is 8.3GB which is 1.02GB smaller than the used space:
Where is the 1GB space going or we say what takes up the 1GB space? It may be allocated for system protection.
System protection is a feature that regularly creates and saves information about your computer's system files and settings. It also saves previous versions of files that you've modified. All these files are saved in restore points, which are created just before significant system events, such as the installation of a program or device driver. Therefore, it is highly suggested that users turn on this feature, but sometimes it takes up so much space. I have seen a computer which allocates more than 10GB space for system protection, but actually several GB is OK. At this time, we can decrease the space by modifying the maximum usage of system protection space. Steps are as follows (take Windows 7 for example): go to Control Panel, view by small icon, and choose System to get the following window:
Then, select “System Protection”.
Next, select local disk (C:) under System Protection tab and click “Configure”.
Now we can see the current space used for system protection is 2.32GB, but we can reduce it by changing the Max Usage to smaller size. Once the space reserved for system protection is used up, older restore points will be deleted automatically to save new ones. The smaller Max Usage is, the less space will be used for system protection. Of course, we can delete all restore points by clicking “Delete” button to release all space, but this is not a wise choice. Here we change the space to 993.6 MB by dragging the slid handle. Then, click “Apply” and “OK” to apply all changes. After all these changes are made, we can see the used space of local disk (C:) namely partition C becomes 7.54GB rather than the original 9.32GB:
Actually, apart from system restore points, hidden files will make our hard drive space “miss” from hard disk.
5.Hibernate File or Page File May Take up a Lot of Space
Both hibernate file (hiberfil.sys) and page file (pagefile.sys) are hidden system files, and they are located in the root folder of the partition where operating system is installed. They are invisible by default unless we enter Folder Options and then uncheck “Hide protected operating system files”:
The hibernate file is reserved by Windows Kernel Power Manager when we install Windows. The size of this file is approximately equal to how much random access memory (RAM) is installed on the computer. In most systems, it is 75% of the total RAM by default. For example, if our computer has 4GB RAM, hibernate file will be 3GB. However, we are able to disable this feature or change the size of hibernate file to what percentage we want it to be.
If you do not want to hibernate system, turn it off like this: run command prompt as administrator, type powercfg.exe /hibernate off, and type exit to quit from the program.
After that, the hiberfil.sys file will disappear from its original place. However, if you want to keep hibernate but hope it to be smaller, try this way: run Command Prompt as administrator, type powercfg-h-size 50% (can be any percentage), and type exit to quit.
Tip: we have said we can change the size of hibernate file to what percentage we want it to be, but it had better not be smaller than 50%. If it is set to be so small, hibernation failure may emerge.
Next, let’s see how page file takes up our disk space. In general, our computer stores files, programs, and other data we’re using in our RAM, because it’s much faster to read from RAM than from hard drive. However, after all RAM is used up, Windows moves some of data from RAM back to hard drive and place them into page file. The size of page file is changeable, which depends on programs you are running and maximum size you set for page file. It is very necessary to enable page file if your RAM is not enough, because this can stop system crash or program failure from happening when RAM is used up. However, some computers are set with too large page file, which is unreasonable and also space wasting. Under this situation, we had better decrease the space for page file or remove page file to save disk space. Detailed steps are as follows:
Go to Control Panel, choose View by small icons, select System, and tap on Advanced system settings to get the window below:
Then, choose “Settings…” of Performance under “Advanced” tab.
Next, tap on “Change…” button under “Advanced” tab.
At last, uncheck “Automatically manage paging file size for all drives” if it is checked, select the drive where page file is located, choose “Custom size”, and then type a new paging file size in megabytes in the Initial size (MB) or Maximum size (MB) box, and click “Set”. However, if your computer has enough RAM to keep smooth running, you can also disable page file by changing both initial size and maximum size to 0 MB or clicking “No paging file”.
Tip: reducing the size of either the initial or maximum page file settings, we must restart our computer to see the effects of those changes.
After changing the size of hibernate file or page file, you may find several GB of disk space back, and this space can be used to save any other files. Next, let’s see the last possible factor which may make our hard drive space missing.
6.Disk Space is Wasted due to Employing Unreasonable Cluster Size
When we are viewing how much space our files are taking up, we may find a strange situation where real file size is 597 bytes but these files occupy 12 KB space on the disk:
What’s the reason and where is the missing space? To answer these questions, we need to know something about cluster size, which is called allocation unit size by Windows.
We can say cluster is the smallest space unit for data storage and management, and cluster size is set when we are formatting a partition. One cluster can hold content of one file no matter how large the cluster is. For example, if we are saving a 100 bytes file to a partition whose cluster size is 4096 bytes, the 100 bytes file will take up 4096 bytes space, and the remaining 3996 bytes space cannot be used to save any other files; if we save a 4097 bytes file, it will take up 2 clusters, namely 8192 bytes space. As a result, occupied disk space is always larger than real file size if this partition saves small files, but fortunately we have a good way to make them take up less space, and it is to decrease cluster size.
We have said cluster size is set when we are formatting a partition, so we can reformat the partition to decrease cluster size. Steps are as follows: open Windows Explorer or enter “Computer”, right click the target partition, choose “Format” feature to get the following window:
Here, we can choose a new smaller cluster size for the selected partition, 512 bytes for example. Once the cluster size is set to 512 bytes, a 100 bytes file only takes up 512 bytes space rather than the original 4096 bytes disk space.
Nevertheless, decreasing cluster size via “Format” command will make all files saved in the target partition lost. If you want to reduce cluster size without data loss, try using the partitioning tool MiniTool Partition Wizard. For detailed to change allocation unit size, please see Change Cluster Size.
Tip: the free edition of MiniTool Partition Wizard does not support changing cluster size, so users need to download or purchase the professional or more advanced editions for this support.
Is your hard drive space missing without knowing an exact reason? Now try taking one or some of these ways to find it.