Thanks for your helps and I am so sorry to be such a pain! I still haven't managed to render audio in blue. I did follow your instructions and tried different combinations of the commandlines but I still get the same error message (the number of the Error = 2 sometimes changes).
DOS now recognises csound when I type it up, and I have also created a batch file so that I don't need to write the whole command every time I want to render audio in Csound. so Csound seems to be fine at the moment. I can't think what the problem could be and one of my friends who has been using blue for a while doesn't seem to have a clue either.
I am sorry to have caused so much inconvenience.