OK, are you in campaign or Multi Player?
If you in SP, then make sure you have Swapped the User Ability of the Sword. However, you will not have a 1st Person View.
In MP, a very good way of getting a usable energy sword with 1st Person is:
Batch Extract the MP map.
Extract BSP
open b40.
Recursivly Extract the Energy Sword.
Save the CSV file, and Extract the raw model
Now, do the same for the Plasma Rifle (yes, i know theres one in the MP map

)
Find Where you extracted the PR to, and rename all the files that have Plasma Rifle in (eg. to Energy_Sword_New)
Replace all the Dependencies aswell, making sure to alter the filenames of the sounds etc.
rebuild the map, anding the 'Energy_Sword_New' and Energy Sword.
Now, Open the map in HHT and Scroll Down To [weap]
Expand, and find Energy_Sword_New.
Replace the 1st Mod2 dependancy with the Mod2 of the orgiginal Energy Sword.
Now, DL Knaves Energy Sword (
http://files.halomods.com/viewtopic.php?t=7418) and follow the instructions for the 2nd Mod2.
now, goto [bipd] and find the MC.
There should be 2 [weap] dependencies.
Change one for the new sword!