How can i delete all 400 images from my camera?

If you're sure you don't want the images on the card any more you could try formatting the card in the camera or on your computer.

If you have deleted the images then the space that was occupied by these images is freed for the camera to place images into the freed areas.
It is highly unlike you can recover these deleted images as they would be over written by the new images.

To delete all information on the card, simply format it using the format command available in the menu.

Hi,

To delete the images from the Camera, press the Play button on the Camera to view the images. Display the images which you want to delete and press the DELETE button (Recycle Bin icon) located below the lower left of the Control buttons.
To delete multiple images, slide the index lever and select with the control buttons.
While the index screen is displayed, press the Delete button and select the images with the control buttons and select Enter button. Now, select the images which you want to delete and press the Enter button to display the Delete icon on the images. Press the Delete button again to delete all the images.
You can also delete all the images in the folder by selecting All in this Folder to delete the images.
To delete all the images in the Memory Stick you can select the Format option from the Internal Memory Tool or the Memory Stick Tool Menu to Format the Internal Memory or the Memory Stick.

Thanks for using FixYa.

Try to format the card in-camera - after saving your images on you computer or hard drive. There are sometimes issues when the card has been formatted elswhere, so always format in-camera.

This sounds like it might be a defective CCD imager. If so, Canon should fix this for you for free, including free shipping both ways. This is regardless of your camera's warranty status. Please check this link for more info.

Applicable cameras include:
A40, A60, A70, A75, A80, A85, A95, A300, A310, S1 IS, S60, S200, S230, S330, S400, S410, S500, SD100, SD110, IXUS V2/300/400/430/500, IXY Digital 30/30a/200a/300a/D320/400/ 450/500

As for your formatted card, see this article next.

This sounds like it might be a defective CCD imager. If so, Canon should fix this for you for free, including free shipping both ways. This is regardless of your camera's warranty status. Please check the following two links for more info:

http://camerarepair.blogspot.com/2007/11/canon-digital-cameras-showing-black.html

http://www.usa.canon.com/consumer/controller?act=PgComSmModDisplayAct&fcategoryid=225&modelid=13390&keycode=2112&id=29819

Applicable cameras include:
A40, A60, A70, A75, A80, A85, A95, A300, A310, S1 IS, S60, S200, S230, S330, S400, S410, S500, SD100, SD110, IXUS V2/300/400/430/500, IXY Digital 200a/300a/400/450/500

This sounds like it might be a defective CCD imager. If so, Canon should fix this for you for free, including free shipping both ways. This is regardless of your camera's warranty status. Please check the following two links for more info:

http://camerarepair.blogspot.com/2007/11/canon-digital-cameras-showing-black.html

http://www.usa.canon.com/consumer/controller?act=PgComSmModDisplayAct&fcategoryid=225&modelid=13390&keycode=2112&id=29819

Applicable cameras include:
A40, A60, A70, A75, A80, A85, A95, A300, A310, S1 IS, S60, S200, S230, S330, S400, S410, S500, SD100, SD110, IXUS V2/300/400/430/500, IXY Digital 200a/300a/400/450/500

Take no more pics until you've recovered the photos, take the card out of the camera. Here's some freeware photo recovery software that should be what you're looking for:

http://camerarepair.blogspot.com/2007/12/recovering-those-accidentally-lost.html

You will need to use a flash card reader with this software. If you don't have one, get one, they're cheap:

http://www.amazon.com/s/ref=sr_st?keywords=card+reader&rs=172282&page=1&rh=n%3A172282%2Ck%3Acard+reader&sort=price

This seems like a card or software error.
If you are using the camera software[from the disc] to upload the images- remove the software[Start/ControlPanel/add/delete software]
Windows does not need software to perform this task.
If that fails
Invest in a USB card reader and always use that to down load images.