Q: 2004 IPOD 40 GB - UNABLE TO CHARGE - HELP ?

Is this a 3rd gen iPod, which has a touch (not click) wheel, and a row of four touch buttons in a row between the wheel and display?  If so, that iPod model is meant to be used with a FireWire port, not USB.  It can only charge when connected to a FireWire port using a FireWire docking cable (which came with the iPod), or connected to a FireWire power (wall) adapter (which also came with that iPod).

Or, is this a 4th gen iPod?  An iPod sold in 2004 could be either one.  This web page shows all the iPod models

http://www.everymac.com/systems/apple/ipod/index-ipod-specs.html

If you can clarify the exact model, there may be a solution.  If it's 3rd gen, do you have the FireWire docking cable and/or the FireWire power adapter that it came with?

That would be one of the variations of the 4th gen iPod.  So, it should be able to charge when connected to either FireWire or USB.  You are using USB, correct? 

When you connect it, does the iPod's screen do anything?  If the battery is currently drained, and nothing appears on the screen when connected, that means the iPod is not getting any power from the connection (unless the screen is faulty).  Even if the battery was bad, when connected to power, the screen should show something.

If your Mac has a FireWire port, and you have a FireWire docking cable, have you tried it with FireWire?  NOTE:  If your Mac has FireWire 800, you'll need an adapter to convert it to FireWire 400 (the older type).

i get on the screen is a picture of the battery with one end shaded in black... Then a do not dissconnet warning comes up. Shortly followed by another message it is ok to disconnect.

That all sounds normal.  The battery picture says it is charging; it is getting power.  It shows the current level of charge, which is low.  Then, the iPod connects to iTunes, and it does the initial automatic sync.  That is when the screen says "Do not disconnect" (because the iPod's disk is mounted by the system).  After the automatic sync completes, iTunes unmounts the iPod's disk, and that is when it says "OK to disconnect."

So, don't get another docking cable, because the one you have seems to be connecting the iPod as expected.  If the iPod's battery does not charge, or it is not able to hold its charge after disconnecting from power, the problem is probably the battery itself.  If it has never been changed before, after ten years, it is likely to be worn out.

I'm not sure if an Apple Store will replace a battery on that model these days, but depending on where you live, there may be local repair shops who can do it.  It is not very complicated.  It takes about 5 minutes, for someone with experience.  The hardest part is prying the case open.

If you are good a such things, this web page has repair guides

http://www.ifixit.com/Device/iPod_Original

For your concern from the first post

i dont want to lose musice stored on.

your iPod appears to be working (except for the battery), so you should be able to off-load its songs (even if the battery is bad).  You cannot use iTunes to transfer song files from iPod to computer (except for songs purchased from the iTunes Store).  However, there are third-party methods and utilities that can transfer from iPod to computer.  If you do an Internet search on something like "ipod transfer," you should get some links.  (The CNET article seems to be popular.)

Once the song files from the iPod are on your Mac's drive, add them to your current iTunes library.  If you get the iPod's battery replaced and it works properly again, or if you get a new iPod, you can sync it to your iTunes library that has all of your songs.

It's odd that a different cable got its battery to charge properly, but that cable does not allow it to connect to iTunes.  The other cable seemed to allow you to connect to iTunes, but it did not charge the battery properly.

You should definitely off-load the songs and add them to your iTunes library, in case there is something odd happening with the iPod.