As long as:
1. you properly burn the DVD image (you should see multiple files/directories on the DVD after the burn, not the .iso file),
2. your PC supports DVD booting (most fairly recent machines - the BIOS must support UDF),
3. your boot DVD drive supports the media you are using (DVD-R, DVD+R, DVD-RW, DVD+RW, DVD-RAM),
...then the DVD will boot. Many people download the DVD image when they can't actually use it. The CD images are a safer bet, as CD booting has been around for longer.