A disk quota is a limit assigned by a system administrator that controls few aspects of file system on modern operating systems. There are basically two types of disk quotas named as usage quota (block quota) and file quota (inode data). The usage quota limits the usable disk space and the file quota limits the number of files and directories that can be created. Mishandling of disk quota by the administrator can result into a STOP error message. Once the STOP error message appears, the hard drive becomes unmountable making all the data saved in the hard drive inaccessible. For complete recovery of data in such data loss situations, an updated backup acts as a boon to restore your lost data. But, if no updated backup is available or backup falls short to restore your lost data, then you need to opt for advanced data recovery software.

As a practical scenario, you encounter the below error message which indicates that quota was returned to a process, but that process was not using the amount of quota being returned:

“STOP: 0x00000021 (parameter 1, parameter 2, parameter 3, parameter 4) QUOTA_UNDERFLOW”

Parameter 1: The process that was initially charged, if available.

Parameter 2: The quota type. For the list of all possible quota type values, see the header file Ps.h in the Windows Driver Kit (WDK).

Parameter 3: The initial charged amount of quota to return.

Parameter 4: The remaining amount of quota that was not returned.

After the above error message appears, the data saved in the hard drive becomes inaccessible. The above error message can also occur when the quota charges have been mishandled by returning more quota to a particular block than was previously charged.


Few measures that help you to overcome the above error message and access the data are discussed below:

* Remove the new hardware and reboot your system.

* Confirm the compatibility of the hardware and drivers by using Microsoft Hardware Compatibility List (HCL).

* Select Last Known Good Configuration option while booting your computer

But, if the above actions fall short to resolve the STOP error message, then you will need to use Emergency Repair Disk. In case, you do not have the disk or the disk fails to resolve the issue, an ideal solution is to reinstall Windows. A clean reinstall of Windows will completely erase the data from the selected hard drive partition. To recover your data after reinstallation process, you will need to go for advanced data recovery software

Stellar Phoenix windows data recovery a foremost data recovery utility. The data recovery utility recovers lost data from corrupted, deleted, formatted or lost hard drive partitions and volumes. The utility supports 185 varied file types. It is compatible with FAT32, VFAT, NTFS and NTFS5 file systems. The utility is designed for Windows 7 (Currently in RC1), Vista, XP, 2003 and 2000

Author:-K MADHAV
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