As TJK says, if you got it from Vstep, that link should work.
Otherwise, it will depend on the policy of the place you got it from. Some vendors allow downloads for a limited period of time. Others allow a longer period if you have paid an extra fee at the time of purchase.
My advice is to always save the download file to a safe place, in case of accidents (on a memory stick or CD for example). Ultimately, it is your responsibility to look after your own software, of course.
This isn't really a technical support issue, so I will move it to Small Talk.
