Welcome to TechSpot young Chris !
As a rule, one does not bother to make an image actually bootable as it stands. One saves the image in a compressed form. This is done with an imaging program which also comes with a method of creating a bootable CD or DVD (even floppy if you have one). Then to replace a broken system, one starts with this independent booter, and restores the compressed image to the partition it came from (or more usually a new HDD!)
One of the best is Acronis True image, whose version 8 was free for personal use. I am not sure if there is a current one which is still free, but with a little googling you could probably fins an older-than-current version which will work just fine. Of course there are other free alternatives, take your pick, but as I say, before using it, make sure you can create the bootable starter.
If you have a C: drive which you also use for data, you will find the image is also rather large (look for 40% compression). In my long experience, an all-round better safety measure is to add a second partition for data, and use the C: drive just for programmes, which keeps it down to 5-10Gb and will image to 3-6Gb. Acronis allows a single image to be split into a number of sub-images each sized to fit on a CD, or DVD whichever you want.
In the main, you are very unlikely to ever need this image, so to use a removeable drive for it is not really a good use of space. My own favoured method is a second internal hard drive, carrying a C: drive image and frequent incremental backups of my data partition(s). This protects me against a complete failure of my main HDD.
During my career, some of the problems I have hit are : images on a second partition of the same drive that failed, taking the image with it; not taking full images often enough, so when the need suddenly and unexpectedly became vital, it was up to a year old!
Good luck in your career - you are showing early signs of significant understanding.
