I managed to win myself a Tom Tom One 3rd edition (1 gig memory) sat nav. It came with Western Europe and UK maps. I live in the UK.

It does not have a memory card - so all maps, etc are stored on the hard disk inside the machine.

I am going to the US next year and will want to take it with me - and will purchase a USA/Canada map for 30 pounds off the Tom Tom website.

Does anyone happen to know how it works - I had a little play - and when I connect to the Tom Tom website via the software that you download - it advises that I backup before I download or change anything.

I have therefore backed it up to my PC. If I purchase the map of the USA - it will not fit on with the Europe and UK map already loaded I assume as the map is 900 Meg in size. I assume it will therefore overwrite it. Am I correct?

If I download the USA map today (currently half price) - where will it be stored? If I then want to use my UK map tomorrow - how do I put it back on? Do I simply restore it? How would I then put the US map back on in a few weeks time? I don't seem to be able to name the backups i.e. UK Map and US Map.

I have never used one before so sorry if I am asking silly questions.