IPad – I can’t see the photos on the iPad mini from Windows 8

You can move the iPhoto archive in your Photos folder in your Home folder to a location on the external drive, create an alias in Mac OS X from the new location, and drop that where the archive used to be in your Photos folder in your Home folder. iPhoto will automatically redirect to the external drive. I do this at home and it works great. As long as that external drive is backed up, you're all set.

Otherwise, you will have to use backup software (not Time Machine in this case) to ensure backups are made from the internal HD to the external hard drive on an automatic, ongoing basis.

You can only access photos in your camera roll via USB, I suspect you added those other albums via iTunes (as opposed to created them on you device with iOS 5). There is no official way to get those photos off your device.

• You can try to find an app that can access your photos and save them to your camera roll (e.g. Photoshop Express, free). This might be a lot a work depending on how many photos you need to copy.
• You could use Dropbox to upload your photos to their servers and download them on your PC. You'll need an dropbox account, but up to 2GB is free. Dropbox allows you to select multiple photos to upload at once.
• If your device is jailbroken you can get access to the filesystem and copy your phones that way.