I have got hold of an old TomTom Go Live 750 and the navcore and map on it are quite old...
was going to update it to navcore 9.510 and UK & Ireland map 1005.8763, Just wondered would be best to install navcore and map on the internal memory or on a micro sd card or on both, which would run quickest/smoothest?

I beleive that External memory would be quicker. (If using a class 6 card or above)
Just make sure that your bootloder is updated to at least v5.5128 so it can support SDHC (Already should be on your model).

Also. if you do it this way, you can simply remove the card and be back to default if anything goes wrong

Hope this helps.

Thanks deano30923 I will do it that way...