ntfsfix is a program that fixes NTFS partitions altered in any manner with the Linux NTFS driver. ntfsfix is NOT a Linux version of chkdsk. It only tries to leave the NTFS partition in a not-so-inconsistent state after the NTFS driver has written to it.
ntfsfix appeared because MS chkdsk is well known for its stupidity when fixing altered partitions. Because the main problems are journal files, ntfsfix aims to fix those issues.
Running ntfsfix after mounting NTFS partitions read-write is recommended for reducing the chance of severe data loss when NT/W2K/XP tries to remount the affected partition(s).
In order to use ntfsfix you must unmount the NTFS partition, and run ntfsfix device, where device is the NTFS partition. After this, you can safely reboot into NT/W2K/XP. Please note that ntfsfix is not a chkdsk-like tool, and so is not guaranteed that it could fix all the alterations provoked by the NTFS driver.