Having updated my own Tomtoms (Win6.5 on a smartphone and TT ONE v3) and my daughter's TT510 (with map on an SD card), using Tomtom Home and the autoactivate maps, I felt confident enough to offer to update a friend's Tomtom one, however now I'm not so sure....

The device was bought about four years ago and is a Tomtom ONE model 4N00.005R, it has a SD card slot but no fitted card. The Navcore is 6.560 and the map is Western Europe v660.1256.
The device has had no attention since being removed from the box.
My instinct is to connect it to Tomtom Home which will probably offer an update of the Navcore and then download and install the appropriate 875 series map with autoactivate. But should this be stored on the internal memory or should I fit a 4GB SD card and put the map onto that?

Expert guidance please

If you want to use a SD card you might have to update the bootoloader as your current bl only supports normal SD cards, but no SDHC.
Updating is the same as you've done before and you can do all on the SD if you like.
You'll find our automatic Navcore installs for 32mb devices as well.
Updating through Home will work too and if you don't need maps with ALG and other extras you can do that.
Patch th Navcore and activate the map when done - keep in mind that you need a ttgo.bif on the SD as well when you try to activate the map.