|No, you cannot create an ISO image of your drive.|
An image of your entire HDD isn't exactly an ISO image. An ISO image holds the file system used on optical media like CDs & DVDs with the exclusion of audio CDs. Also, the average size of a hard disk in a typical home PC is several times larger than the space available on an optical media regardless of the sophistication & type of compression implemented. While you can span the image across multiple DVDs, it's far easier to have a secondary drive to which the primary HDD image will be stored to start with.
FYI, there are many programs out there to generate a clone image of your local drive(s) ... as hinted by XPUser in response #2. The most popular ones aren't available for free, but there are many that are available for free, like, DriveImage XML; Macrium Reflect; XXCLONE; GImageX; Clonezilla; G4L; Clone maxx & so on. It all depends on your cloning/restore preferences & level of sophistication.
Jabbering Idiots: Everywhere You Look!