External hard drive - iPhoto pops up

Hi charlesibook,
For right now, use Image Capture to change your preferences to not have anything open when your camera (in your case, your external) is connected.
This will stop iPhoto from opening for now, but we still need to find out the reason why this is happening. By the way, I use Image Capture to download all my photos, then I can choose which library I want to import them in after.

iPhoto: How to Change the "Open Automatically" Preference

If you change the preference to have Image Capture open when a camera is connected, then that's what will happen.
You can download the photos through Image Capture, which automatically puts the photos in the Pictures folder. From there you can put them in a dated folder and import them into iPhoto. Depending on what library iPhoto was using last, that is where the photos will be imported.
To give you a scenario:
I have three libraries. My main library, a wedding library, and a library for my daughter.
If I just downloaded some photos from my daughters camera, then I will want to import them into her library. I launch iPhoto with the Option key to switch to her library and then once opened, I import her images.
I don't have iPhoto open when a camera is connected because i don't want photos imported into the wrong library or the library that was last opened by iPhoto. I want to make my choice after I review the photos.
It's an extra step, but, it's the way I like to do it.
Adding to this, I also have an easy way to just backup my photos on an external drive.
Every time I download photos from Image Capture I put them in a dated folder with identifying text. After I import the folder into iPhoto, I drag the folder to an external HD for backup.

so to answer your last question, no, iPhoto will not open when your camera is connected if you have set Image Capture to open, or another application, or chose "nothing" to happen when a camera is connected.

I can tell you that if you chose Image Capture to open when a camera is connected but also happen to have iPhoto open at the time, then your camera will mount within iPhoto and ask for you to name the roll to be imported and then you can import it with iPhoto.

I am hoping nothing will pop up...
Try it an see.