Hi!
I run Linux as my desktop (some glitches but the main stuff such as firefox, libreoffice, mail client, and media players work well).
This is a 64bit processor with 4GB ram.
I have two hard disks. first is 1000GB and second is 500GB.
I downloaded windows 10 iso image from microsoft website. Google says if I don't enter a product key, then it will give me a trial mode. Trial mode is fine as I only need to test some stuff. This will only take a week or so.
Virtualisation is out of the question since this CPU doesn't support KVM.
I flashed the iso image in a computer running windows 7 in an internet cafe to two usb disks (one 8GB and one 32GB).
I tried booting them and both lock immediately after showing the windows 10 blue logo.

I tried another thing. I flashed the iso to a ntfs partition then added a GRUB entry to boot it.
It booted but also immediately locked up at the windows blue logo.

so far I have tried:
- Windows 10 64bit english iso.
- Windows 10 N 64bit english international iso.
Any idea how to debug this?

The last windows I used was good old windows XP in 2004 so I am quite out of date.

Would the 32bit image be worth downloading? Does Windows kernel support PAE to use the full 4GB ram? It is possible that one may boot?
a month later
it seems to me that either your pc doesn't have the minimum requirements for windows 10 or the windows 10 image you downloaded is corrupted due to a connection problem, try downloading it using torrent.

But if you think it's a booting problem try

https://sourceforge.net/p/boot-repair-cd/home/Home/
You can always buy a Windows 10 installation disc for 3000LL to 5000LL if you want from any CD/DVD Shop.