What program are you using burn the dvd? And does it tells you where it saves the temp files for creating the dvd image? That would be where it most likely is still residing on your HDD and taking up space. The next time you use the program - which I don't know what software your using- go and find that folder and delete it and you should get your space on your HDD back. But make sure in the future burns if your software has option to check the box so that it deletes the saved temp files on the HDD so you get that space back.