that sounds like a bit long but i might let it go another hour
can you see the hard drive led that flashes when the hard drive is in use. it usually looks pretty random. If that is still going than the process is still working. If it is pretty much stopped than the thing is probably stuck
when you decide it is definitely stuck see if you can just get out of it by hitting cancel or if there is a little x on the top right of the box. or you can hit alt F4
or if you have to you hold the power button in for a few seconds till the computer turn off. then turn it on again.
hopefully it will at least go back to where it was before you started installing the new operating system
at that point you can
A. decide its not worth being a guinea pig for microsoft to test their new op and leave things as they are.
B. try the download again making sure that your anti virus is off and everything else is closed
you can create a windows*****using the program that you download from this page make sure that you select the option to create a flash drive for use on other machines
using that flash drive you can install the win 10 operating system
no matter what i recommend making sure the computer is backed up before instaling the win 10 again.