what exactly do you mean by software. Is in DPP, Image viewer or zoom browser. (or the whole package)
Canon 300D CD and software version are very old. The problem with this case is that canon does not allow new donwload of latest DPP versions but allows free updates.
And your 300D software cd is not compatible.
here is a work aroundhttp://www.northlight-images.co.uk/article_pages/install_canon_software.html
follow the article..it works like a charm. No worries to change setting in camera. hope this helps