I don't think I can describe to you what you are going to see step-by-step because, as I said before, I do not now - nor have I ever - used mandrake. Most likely, you will need to delete hda8 and hda7 and then resize hda6 to take up the unalocated space that was created by deleting them. How the partitioner will present these options to you is not something I know for certain.
Remember, this is only a suggestion. You don't have to do this, but I think you will be happier in the long run this way. If it causes you too much anxiety, then leave it be until you are more comfortable with linux.
While I admire your desire to be prepared, sometimes you just need to jump in and hope there's water in the pool. Only way to learn. Do a search here and on the web. These are not new questions. The Mandrake site probably has some howto's as well.
Oh and don't forget to back up what you can't afford to lose.