Forget 4.05, if you have a PSP 1000 use 5.00 M33-6 or Gen. Or you can have the easy option of just updating to 6.20 and installing HEN CFW on any moder PSP.
EDIT: For 6.20 firmwares it's TN (Total_Noob) or 6.20 PRO (B-6 is the newest although B-7 is out it's not a official CFW, it's a 'Nightly Build'