After a week of trying, snooping around forums, genius brain farts, I got tomtom working on my Sony NV-U71T.
What do you need;
Looks like the Sony NV-U71T has a small version of WinCe 4.2 which support TomTom 7.450 and not 7.910.
On this site you will find the necessary software. Install it to your device as descripted.. tutorial demonfatal.
After installing the 7.910 i got a message "This version of TomTom is not supported ...