The image would not fit on a single DVD. You are better to have image file stored on an external harddrive and use with the image programs boot CD/DVD (which you create and burn)
There are lots of free programs and usually the harddrive manufacturers provide a download of their free version of Acronis True Image or similar.
Western Digital Acronis True Image WD Edition Software http://support.wdc.com/product/downloaddetail.asp?swid=119
There are other programs available to download and others will prob suggest them. (I use Acronis)