The mp3 folder goes in the root of the unit, so that if you were to do another screenshot, you'd see a mp3 folder just as you now see a art folder, an asr folder, etc. Put the files in the mp3 folder (all lower case, no quotes). You do NOT need or want a folder called simcard.
What kind of 2 gig sd card do you have? It should probably a sdhc card. It should be already formatted as fat32. If it isn't, do so with the sd card in the unit. Format it with Explorer. Make sure you are formatting the sd card and NOT the internal storage of the TomTom.
However.........
If you put the card in the unit, turn the unit on, dock it to the computer and start Home...if Home asks whether you want to use internal storage or external (sd card), then you don't need to format the sd card. The unit already 'sees' it.
But..........bottom line, do NOT put a mp3 folder in another folder, either in internal storage or on a sd card.
And why do you have a folder called 'poi'? All custom or dl poi's go directly in the specific map folder for which you want them to show..in your case, more than likely 'North America'. I hardly think you've gathered poi's for Guam. <g>