I have a TOMTOM G0720. I have installed the home program on my XP computer but every time I try and connect the Tomtom by the docking station USB the computer program tells me that no TOM TOM installed/connected.
Have you clicked "connect to computer = YES" on your sat nav? When you plug in the USB and turn the sat nav ON it should say "connect to computer" with a "yes or no" option. Must click yes then it will probably install itself on the PC. Then open up Tom Home.
Check you device manager. If you see a USB device with an ! next to it. uninstall drivers and reboot the machine. Drivers should auto install on startup.
This happened to my GO730T after I downloaded updates. I called TOMTOM and they recommended that I took the unit back to the supplier for a replacement which I did. The new unit did the same but I did notice that when the unit was switched off if I took out the SD card (I purchased one for all the MP3's I wanted to load) and refitted it then connected it to the dock and switched on it was recognised. A bit of a nuisance but it works.
Hope this helps