Sounds like you either removed the SD card when the PC was writing to it, or put into the TT with it powered on.
Unless you have a CD with the software and maps (not sure if this comes with it or not as STD), you need to send the mem card to TomTom to fix - unless TT Home has an option when you register it.
Why didn't you browse the TT mem card when it was connected to the PC? It shows up as a mass storage/mem reader and you can see everything on the card without having to take it out of the TT.
You might be lucky and be able to use the smart recovery tool fro
www.pcinspector.de, but I think you've likely corrupted the data beyond recovery.
Curiosity, cat etc
