tomtom start sd card help

I have just bought a 4Gb MicroSD card for use with my new SatNav, inserted into the unit and allowed it to "Format" the new card by answering "yes" to the TT on screen window. I was hoping to put truck map on, when I connect my sd card to my PC and I cannot see any extra memory space,

I have also noticed when I take the MicroSD out of my "TomTom Start 25" and put it into a 'USB card reader' Windows 7 reports that there is no free space on the new TomTom formatted MicroSD.

I can reformat the MicroSD again using Windows 7 and this restores the full SD card memory back to capacity but re-inserting it back into the "TomTom Start 25" displays the need to format to "TomTom Start 25" specification again.

I apologise for this long winded post but I thought I'd best give as much detail as possible.

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