Please can someone help me out here.. I have watched tutorials on how to take your xbox 360 apart and I successfully done this in like 5 mins

I have watched cofree1234 video on how to flash the BenQ with iprep and I wanted to try and upgrade my ixtreme 1.4.1 to the 1.5.1.. I did everyting and bought everything necessary.. I purchsed the Xecuter CK3 PRO and hooked it up to my pc and also loaded the 1.5.1 bin file in iprep and created a boot on my 4GB flash usb stick.
Now here is where it starts going down hill for me.. I boot up on the flash and I then type:
C:\>dben 1234567 12345 then press enter and it says:
ERROR: BACKUPS\1234567\12345\BenOFW.bin does not exist! Program Aborting..
I thought it may be because I do not have a VIA VT6421A PCI PC Raid Card .. However I am connecting the SATA cable onto my motherboards port and it is detecting it in BIOS .. so could this be the reason?
When I purchsed my xbox 360 I bought it flashed with ixtreme 1.4.1 and I still have the Ben-OFW.bin and the Benq-CFW.bin file.. do I need to flash to original then flash to the 1.5.1? Please can you guys help me?
Or shall I just buy a VIA VT6421A PCI PC Raid Card and try it again? Thanks..