Have found lost maps etc in computer, how do i get them from computer back into the device xxl

By dropping out I am assuming you mean it freezes up and turns off.
If this is the case your XXL has an incompatible bootloader and requires updating. This will be the case even if you updated it via tomtom HOME. Back up your map, voices and zip then reformat and reinstall navcore

no. only deletes settings, maps and navcore remain

First, register your new navigation device:

1. Go to www.tomtom.com/getstarted.
   
2. Select your country, then click on Get Started.
   
3. Follow the online instructions to install the necessary TomTom HOME software on your computer and update your new navigation device with the latest maps.
   

you will need to download a totally new map that is specifically designed for trucks, which indicates low bridges , truck stops, etc. Tomtom do sell them

remove some files from map folder example: cspeech_FRA.dat,cspeech_*.dat

Theres good news for you, you can get a SD card for your tomtom, and all you have to do is to install or download your maps on the SD card then fix it into your tomtom and you will be able to view your maps from there. For the lost maps, connect your tomtom to your computer, be sure to have your drivers software, then you select your tomtom form your computer, then you install all lost maps back on it by restoring all old maps. But for large downloads, download all new maps on a SD card. That should do the job.
Hope this information came in handy.

here you can get the updates
http://www.tomtom.com/en_us/products/car-navigation/xxl-540-series/index.jsp#tab:maps
good luck, and do rate the solution if get help

it sounds like you may have just deselected the maps.

go to tools settings map then map info(bottom of the screen)

check that there is a tick next to your mapset if not just tap the name of the map and you should be sorted out.

If you are referring to Latitude and Longitude , yes. You can use those co-ordinates to navigate to a destination. This especially works fine in countries where the Avenue and street information is not available. Google maps can give you the latitude and longitude coordinates. You can fed those into the GPS and navigate. Please note, you will need the maps of the region involved. Click (Tap) on the main screen. Tap on: navigate to Tap on : arrow Tap on: Latitude longitude Enter latitude and longitude using keyboard, Latitude first and longitude next. Be careful while you do this and do not forget to enter the directions North, West etc.

For the TOMTOM XXL540 while connected to your PC hold the poer button down for about 15 or 20 seconds the device will shutdown then restart when reset