I've had a little look around the web about this but can't find much. I'm think about win 10 but my system originally had vista on, I upgraded to 8 then 8.1 . if I wanted to do a clean install with win 10 will I be able to do it with just 10 or will I have to do vista, >8.1>10 as they were all upgrades. Can I make a bootable copy of win 10 onto a pen drive or something so I could do a clean install in the future.
I think you are all set, all you need to have handy is your license number, I believe it would be the one that came with your Win 8 upgrade. Make sure you have signed up for the free upgrade first, you do not have to upgrade until you ready but you must sign up before the free period ends to be eligible. If you go to the download Windows 10 page (http://windows.microsoft.com/en-gb/windows-10/media-creation-tool-install) and download the tool it will offer 3 options, either upgrade right away, make a an ISO for burning to DVD or make a bootable USB (USB drive size should be 4gb or more). I upgraded but I think if you boot from the media then it will give you an option to do clean, else just clear your system disk and it certainly will.
From what I've read you have to do the upgrade first then make the fresh install media if you don't the clean install won't activate