The red cross means that there is no navcore on the SD card. The 500 has no internal storage.
Use an SD card from 2GB or less to try it out.
*) Recommended Navcore navcore 9.540 32MB device
topic17200.html --
Recommended Map (meta availble)
United Kingdom and Republic of Ireland 965.7250
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1) Make a backup of your Device and delete the content.
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2) Unpack the* navcore (winrar ) and place folders and files on your Device Internal/SD Card.
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3) Reset The Device (minimal 20 sec) and start it till the announcement "No map found"
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4) which map is compatible with any NavCore.
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maps-v9xx-f179/all-new-maps-965-966-t18262.html --
Horizontal map version
Vertical navcore
From navcore vertical down and horizontal maps
If the box is green you can use the map with this navcore (if it is red not)
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5) Be sure that you have the right map.
Is there a meta from the map you want to use.
No meta then you can not use the map.
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Copie the chosen map to your Device (root internal/SD Card) in his own folder.
If you open the map you see the loose files and probably a folder (brand).
Not a map in a map.
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6) Copy "FastActivate.exe" to your TomTom device root (internal or SD Card).
Run "FastActivate.exe".
Select 1 and 2
Done