I would definitely make an ‘image backup’ of your current OS partition/drive before upgrading to Win10.
That way, you can return to the ‘image’ of the previous version, if disaster happens during the Win10 install.
I currently use Macrium Reflect Free for Home Use edition to create ‘image backup’s on a USB external drive.
http://www.macrium.com/reflectfree.aspx
My experience is with Acronis making Win7 backups at home.
these installed would always be kind of glitchy and not a rock solid as the original install.
It's really easy to make the system image that way. In the process, you will be asked to make a restore CD disk. Do it, you need that to boot the computer.
Here's where I had trouble. When booting from the restore CD, Windows can't find your USB hard drive if it's a USB 3, but can if it's USB 2 or older. I copied my image folder (24 Gig) to an older USB 2.0 hard drive and then the restore program had no problems finding it.