Thanks Gidders. You know I will have to kill you if I tell.:D Its a 30D I am at the point of not wanting to take to manyphoto's in case my shutter fails.

My finding on using a compact flash card from another camera.

1. Before using the card, go into My computer and go to the compact flash, there should a directory DCM, delete this directory this will also delete the folder within this directory. Now the card is blank with no directories showing.

2. format the card on the computer, I don't know whether this is necessary but I did it anyway.

3. Put the totally blank card in the camera and do another format. Done.

4. Whichever camera you put the card into it will take on board the last file number and create the directories and folders that is in the memory of the camera.

5. If you are in the field and are using two camera's and have to switch cards from another camera, then you will have to do what gidders suggested to rectify the wrong file numbers, this should put the directories to what they should.