I agree with Mardy - don't bother with the garden planning CD. I am in the processs or re-doing my garden. I started out with the garden planning software - got frustrated because it often did not have the plant I wanted despite having loads on and also the designs you could use were quite restrictive and not that inspirational. Went back to good old pencil and paper to design the shape I want it. For inspiration I have been buying gardening books from charity shops and flicking though them - have ended up with a hotch-potch of all different elements so it will be totally mine.
As far as choosing plants go to the garden centre and wander around going I like that think I will have one of those and then when I get home look them up in my book to check size they will grow and if they loose their leaves and from there decide where I am going to put it.
I have had a lot more fun doing it this way and don't have to spend my time getting frustrated with the computer because it won't do what I want