When I turn on my TomTom it says no maps avaible. When I go to load the canada usa maps I just bought it says not enough memory. How can I reset my Tom Tom back to the maps it had.

Since you have just bought it, you are eligible for a new map (within 30 days of purchase). Please update the map as early as possible. Please follow the steps mentioned below:
Tom do not seem to overwrite the existing map file. So before trying to install the map, you need to delete the folder that contains the map. (It is important to read the next part before you delete the map folder). Once you have connected your TomTom to thecomputer, close the TomTom home window. Double click on my computer. You will see the TomTom hard drive as a drive (like you see the CD drive). Double click on that . Once the folders of the TomTom hard drive opens, look for a folder named USA_Canada_and_Mexico_P. (Please note: this name is for American continent. For others, this name will be different). Right click on it. click properties. Check whether the size of this folder is approximately around 1.3 GB to 1.5 GB. This is just to make sure we have the correct folder. After confirming this is the map folder, copy this folder to your computer for back up purpose. Once you have it safely in your computer, delete this folder from the TomTom hardrive. Go back to TomTom home software. Use the map guarantee to update/Upgrade the new map. You will see this time around the installation completes without a problem.