Getting the path to the user's desktop under Windows is tricky if you're not using Java 1.6 and above.
Looking for a solution around the web, I see many people recommending to use a wrap around the Win32 API using SHGetSpecialFolderPath or reading the value directly from the host registry system as suggested here: http://stackoverflow.com/questions/1080634/how-to-get-the-desktop-path-in-java
But I'm not very fond of these solutions and found one that is simple and seems to work fairly well although it doesn't seem to be documented (yet).
Just try this snippet under a Windows machine:
FileSystemView filesys = FileSystemView.getFileSystemView();
File roots = filesys.getRoots();
And you should be able to get the desktop folder as expected. Under my language, this folder is called "Ambiente de trabalho" so it worked like a charm.
This tip comes from Russ Bradberry: http://stackoverflow.com/questions/570401/in-java-under-windows-how-do-i-find-a-redirected-desktop-folder