Ok. It's been months since I've had to do anything in Java and I forgot the first bit you do, The classpath or getting into the right folder or whatever. So, this guy set it up for me and I used to have to just type JavaFiles or whatever... That's the name of the folder with all my java files.
This was in environment variables - C:\Program Files\Java\jdk1.6.0_27 ...? If I'm going to the folder in explorer I go to Local Disk (C:)/Users/Maire/JavaFiles.