Angels have the Phone Box
But, Microsoft did not intend the user to have 2 operating systems for the price of one. You either have 8 or you have 10.
When upgrades fail early on, it is a sign of driver issues, or recovery partition issues. Error 80070003 is usually an indication that you have messed around with the partitions in W8.x, and W10 can not upgrade because it cannot create the rollback.
Best to backup your data, get out your program disks, locate your keycodes and do a clean install of W8, then upgrade.