TomTom One starts with initial splash screen, then starts with what looks like a diagnostic screen showing numbers 1-8 and some functions. Most function seem to work in diag screen, with the exception of reset. Reset (#8) runs then shows File error!! MD5 no check!! This is a new unit that has never been used, but I do not have a receipt. It was bought last Christmas, but never used until a couple of weeks ago. Any suggestions???
Try a hard reset of your unit. You don't say which model One you've got, but first check to see if there's a tiny hole in the bottom adjacent to the USB connector. If so, gently give it a push with a paper clip for about 5 seconds.
If you don't have the reset button, press and hold the power button for about 15 seconds.
One of those may set you right.
If not ... There's still hope.
Connect your unit to your PC. Home will be installed. When you get the chance, just shut it down with the little "x" in the upper right corner.
Using your PC's OS (Explorer, Finder, whatever, see if you can spot a new 'external drive' that's called TomTom. If so, try to open the 'drive'. There should be a pile of files and folders there.
If you can get connected and can see the contents of your TomTom, we may be able to get it back on track.
Please advise which actual ONE model you've got.