problems in installing windows 8.1 after installing windows 10

[rullll1]

i have decided to use windows 8.1. i downloaded from microsft and used to rufus to make the usb bootable. For some reason after choosing to do the upgrade installtion it says i should restart the computer and re enter the instaltion media( i dont remember the exact words and as you probably noticed english is not my native langauge). so i tried to do the uprgade installion when the windows is on but after choosing the upgrade installion it said that something went wrong.
So i tried to the custom installion and tried to format the disks it gave me this error: error: 0x8004242d

Thanks in advance

 

[Rocky Bennett]

Try it from a DVD instead, it should work easier.