First start here:
TUTORIAL: Clean Install - How to install the latest map and navcore from scratch!
The tutorial gives you step by step instructions. The maps you are after would be for your official 7.903 navcore, therefore they are the basic maps without IQ/ALG. Here is the map thread link for the Australia 900.4600 map:
Australia_900_4600 LINKS ONLY
The Western and Central Europe map is just over 2.4GB, so it may just fit in your device. Here is the link below:
Western_and_Central_Europe_2GB_900_4600 LINKS ONLY
Better would be to use a smaller Europe map, covering the area you really need. Look in the Map Thread Finder below for the various Europe maps and sizes:
Map Thread Finder - Tomtom v900 Maps
VERY IMPORTANT: Make sure the map you are selecting does not say "no meta yet." If there is no meta for a particular map, then it cannot be activated, so do not download it for the moment.
Another post with download links where you can get the above maps can be found below:
All new maps 900 Collections Only