the thread i was looking for involved someone in the same situation who could not get classic to install without classic already being on the disk. if his is part of your problem there are some work arounds, easiest ones being if you have more drives or an extra cd reader likea cdrw. if this is part of issue let us know and we will address that, otherwise i believe slur is totally right and you should have no problems or worries. you can even reinstall osx over osx and not lose your preference settings for it - i know because i've been there, done that.