Hi
I have a TomTom one v1 running navcore 8.395 and Map Truck 840.2554 on a 4gb sdhc card, bought of ebay and works very well.
I would like to upgrade my TomTom one XL to take this card but I’m not having much luck !!! I have formatted the one XL and made back ups of the sd card. But all I’m getting on the XL is the red X on an sd card symbol !!! when turning it on with the sd card in the slot, any ideas please.
Many thanks 
Give this site a go( gpsunderground.com)
Thanks, great site all sorted 