Editing NTFS Sparse Files
If you happen to notice a file that is larger than the disk it resides on – don't worry, your file system is not corrupted. It is just a sparse file. A sparse file contains huge blocks of zero data that are not stored on the disk – the system keeps the track of non-zero data blocks and stores only real data.
FlexHEX fully supports sparse files. On the screenshot above you can see a sparse zero area (shown in grey). The Regions pane in the lower left part of the program window displays the actual layout of data areas. The file is more than 250 megabytes large, however it requires only 64 kilobytes of disk storage.
As with other navigation panes, you can click the area Start or End address to go there, or click the Size field to select the whole area.
If you want to learn more about sparse files, you can find exhaustive information in the article "NTFS Sparse Files For Programmers".