Windows XP command line defragmenter

The Windows XP command line defragmenter is defrag.exe.
If you open a CMD prompt and type defrag /?, the following is displayed:

Usage:
defrag [-a] [-f] [-v] [-?] volume drive letter or mount point (d: or d:\vol\mountpoint)
-a Analyze only
-f Force defragmentation, even if free space is low
-v Verbose output
-? Display this help text