BeOS 5 includes a new filesystem integrity checking tool called chkbfs, which can examine your filesystem for lost or misallocated blocks and repair them automatically (if you purchased the Pro Edition of BeOS, chkbfs will have run automatically at the end of the installation process).
To run chkbfs again at any time, open a Terminal and type:

chkbfs /boot

Substitute /boot with the name of any volume. Errors will be repaired automatically. I recommend doing nothing else with your computer while chkbfs is running.
If you want chkbfs to run a test without actually making changes, use the -n flag. You can also use the -f flag to force free’ing blocks even if there were problems.
Users who have encountered the occassional unremovable file should find that particular long-standing problem cleared up at last.