The USB key app will look for an 8GB partition or USB key, so if you have a larger than 8GB USB key you can make one 8GB partition for the installer and another partition for other purposes. If the key is 8GB though, the whole key will be used. In either case the partition you choose will need to be formatted.Thanks. I bought a brand new USB stick the other day which I'm gonna have to use for the purpose. Do I have to reformat it completely?