How do I delete read-only files from a SanDisk SD memory card?

I put a new SanDisk SD memory card in one of those digital photo frames and then posted pics to the card via USB directly from our computer.

Now I can't delete the photos using the built-in software on the frame or even see, much less edit, the contents of the SD card using any computer.

I've tried three different laptops and a digital camera just for kicks. All three computers recognize the card but show no content. Yet when I put the card back in the frame up pop our pictures.

I want to delete the entire contents of the card and start over.

Format it.

You're using a card reader to put things on the card right?

the best way to do this is by clicking my comptuer when u enter ur card.. and then an icon should come up that says SD Card or something similar and then right clikc on that and then click format... and then click start.. and then it will delete everything (it will go quicker if u do a quick format)