How do I delete all the currently stored photos from my Nikon D70

Try formatting the card.

you likely have too may photos stored in its memory.. download the photos onto a pc, and then delete the photos from your camera.

GT Recovery for Windows Download: www.gtrecovery.net

GT Recovery for Windows is a professional data recovery for PC and Android phones. It can restore deleted photos, videos, audios, documents from PC.

Whenever you lost important photos or deleted photos by accident, you can use it to scan and recover the photos on your phone.

If you had a PC there are plenty of options to recover deleted pictures

This is the best I could find:
http://www.any-data-recovery.com/topics/photo/recover-pictures.html

You can try to recover photos deleted from Camera with a camera photo recovery software, recommended asoftech photo recovery as it helped me many times. you can see more info about photo recovery software from facebook:
http://www.facebook.com/pages/Asoftech-Photo-Recovery/126127714100611?sk=info

Here's video tutorial for how to recover deleted photos from camera

yes, you can recover deleted photos from camera with asoftech photo recovery program.
http://www.asoftech.com/apr/index.html

You have to use a card reader either on your computer or an external USB card reader. Put the card in the card reader, open the recovery program, then select the drive where files are deleted, then press "Start" and wait for it to do it's magic.

Guide to recover deleted photos from Nikon D70?
Connect Nikon with PC
Using a USB cable or putting SD card into an SD card reader to connect Nikon with Computer.
Scan Nikon d70- Running the Nikon Photo Recovery,you can choose Nikon media drive and click "Start Scan" for scanning
Recover deleted photos
After scanning, you will see all recoverable media photos and videos with file type. At last, click "Recover" to recovering deleted Nikon D70 photos.
This Photo Recovery also can recover all photos files from Nikon D3100 like JPEG, BMP, TIFF, GIF, etc. Support all Nikon camera.
For full details please refer to Nikon D70 Manual.- https://guideusermanual.com/product-name-d70-manual&po=4425&lang=English

I had the same problem. I can tell you that in the "System" menu, there is a place to delete all of the existing photos. You have pictures stored on the memory card and also the capability of storing a limited number of photos on the camera's internal memory. If its in the internal memory, that's when you have to find the system area. If the pictures are only on the memory card, then its easier to delete because you just select "format" and it will format the card and delete all of the photos from the card.

It's not necessary to delete the previous scanned photo. To scan another slide, place it in the scanner and press the PREVIEW button.