If you have 3mb free, it soundslike you don't have (m)any apps installed.
In that case you may want to try a hard reset, search the forum for details on this. This will leave your phone like when you picked it up for the first time.
Do a backup to your PC first, and then a restore after the hard reset. The restore recovers data like contacts, calendar, c++ apps (not java - search the forum for how to edit the backup configuration to include java files and midi files, if that's important for you.