FloppusMaximus says in a post on UTI:
  Here's a program to patch the OS [to fix the Defragmenter]. It should work on every current 83+/84+ OS; no idea about the Nspire.
  Not being Brandon, I'm no longer up-to-date on the safest methods for unlocking Flash, so I will simply defer to his wisdom and use FlashDrv. :P

  Disclaimers: this may destroy your calc and/or eat your children. Use at your own risk. 


How to apply the patch:
  Send flashdrv.8xk and fixdefrg.8xp to your calc. Install FlashDrv then run Asm(prgmFIXDEFRG). Asm( can be found in the Catalog.
  You can delete the app and program afterwards if you want to.