How to Clear picture off a Digital Camera?

I took a picture a few days ago,and i deleted it from the digi camera, but i took a picture last night and when i put the lead from camera to pc and the software popped up for it, i seen the pic i had to a few days before!.
i just wanted to know how to get rid of the pictures, is there a way to clear a digital camera memory card, or when you delete them from the actual camera itself, do they go forever. the pc is not mine and neither is the camera, and the pic which i took was rude, and if my friend finds it they will kill me :(
any help before i get killed :p

Hmm, i did the drive selection thing (sorry im not good with computers :p)
and yeh, i took a pic before i posted the comment here, and now its just that pic, not any rude one :D
hopefully that it is coz i had a panic attack last night!.
and i will NEVER take a rude pic again.
Thanks for the help :))

If you are able to connect it to the computer and see a serparate drive in My Computer you can select all the pictures and delete them.

On the other hand, you should be able to delete all pictures from the memory chip or format it using the On-Screen-Menu(OSD)

There is a Delete option in every digital camera, and usually when you Delete, the picture is deleted and there are very few chances of the pic staying there. You can check after you delete, if the pic is still there or not. Do it again if you find it still there.

if you are that scarred buy a new memory card

make sure you are clearing the card instead of just internal memory