All the presets for the synths before Jupiter-8V are stored in the program folder (ProgramFiles). Jupiter-8V and all the synths that where released later have the presets stored in the application data folder (ProgramData). Till Jupiter-8V the presets folder is named "save". P is the project, B is the bank and I is the instrument or preset (before Jupiter-8V). Finding your user presets is somewhat difficult and you should always use the preset export to back-up the user presets.
If you uninstall one of the synths, all the projects (presets) that where not part of the factory presets (installed during setup), are left on your hard drive.