Custom will be fine for what you want. Using third party programs to format makes that data un-recoverable by other third party programs. IE, you're selling the computer and don't want somebody to be able to recover your data.
If you use custom, that data is still technically there on the drive in a raw form but windows won't see it. You'd need a third party program to recover it, so; just use custom.
Which third party programme do you recommend. My external hard drive is also recognized as a RAW drive and what is weirder is the computer thinks this is a CD drive.
If your asking what third party program I used, it was dban. It will wipe everything on the drive. I needed a fresh start, which is why I used it.
Going to give that programme a shot. Thank you much. I have no problem deleting the files off the drive.