reinstalling Vista OS after replacing hard drive without disc

The hard drive on my Inspiron 1520 recently fried and had to be replaced. I have all the discs that came with the computer but there is no disc to reinstall the Vista operating system. As a temporary solution I used a window 7 OS disc that cam e with a new Dell computer that I ordered so that I could at least have the computer work until I coud get this resolved. Is there anyway that Vista can be downloaded through Dell so that I can have the original operating sysytem on this computer without having to purchase it from Windows?