My File Name Number is back to zero and I don't want that ...

Let's review the order of events:

* An initial file numbering sequence is established by shooting a set of photos.
* Subsequently, a CF card with a higher file numbering sequence is used. The EOS digital SLR resets its internal file numbering system to the new numbering sequence.
* The user wants to revert to the initial file numbering sequence.

If this is the case, then the correct procedure to get back to the original file numbering sequence is going to depend on a couple of conditions.

CONDITION A: The user still has a CF card with images that are exclusively from the initial file numbering sequence, ideally from the end of that sequence.
In this case, use the following procedure:

1. Find a spare CF card that you don't mind formatting.
2. Set the 10D's file numbering setting to Auto Reset.
3. Format the spare CF card. This resets the file numbering sequence to 100-0001.
4. Set the 10D's file numbering sequence to Continuous.
5. Replace the spare CF card with the CF card that has the last image from the initial file numbering sequence. The 10D will resume file numbering from that point.

CONDITION B: The user no longer has a CF card from the original file numbering sequence.
In this case, use the following procedure: (Please note, this procedure requires a card reader.)

1. Find a spare CF card that you don't mind formatting.
2. Set the 10D's file numbering setting to Auto Reset.
3. Format the spare CF card. This resets the file numbering sequence to 100-0001.
4. Set the 10D's file numbering sequence to Continuous.
5. Take a photo on the spare CF card.
6. Remove the CF card from the camera and mount it on your computer's desktop via the card reader.
7. Open the DCIM folder and locate the folder named 100CANON. Open this folder to locate the image named IMG_0001.JPG.
8. Rename the image to the desired sequence number, i.e, one number higher than the last image from the original file numbering sequence. For example, IMG_0238.JPG.
9. Rename the 100CANON folder to the desired folder name. For example: 204CANON.
10. Place the newly renumbered CF card in the 10D and take at least one shot. The camera's file numbering sequence is now reset as originally intended.

A few other tips:

All of this is unnecessary if you decide to rename your files with Canon software such as File Viewer Utility or 3rd-party software with file renaming capabilities.
If you really want to keep the camera's file numbering sequence intact, be very careful to control exactly which CF cards you are using. Only use your own cards with the desired file numbering sequence.

As a matter of general "good housekeeping," consider following this procedure which is slightly amended from one posted here a few weeks ago by Richard Smith:

1. Start by locating the CF card that has the most recent image from the file numbering sequence you wish to preserve. PUT THIS CARD IN A SAFE PLACE AND DON'T LOSE IT.
2. Gather all (ALL!) the rest of your CF cards in one place.
3. Set camera to auto-reset.
4. Format all (ALL!) the rest of your CF cards.
5. Set camera back to continuous.