If you want to try out Windows 10 on your machine (and not within a virtual machine) and only have Linux operating systems around you and no DVD burner (or don’t want to spend a blank DVD) and a 4.3 GB USB drive you may want to follow this guide.
You can download the “Windows 10 Technical Preview ISO” from Microsoft for free as long as it isn’t released. Grab it from http://windows.microsoft.com/en-gb/windows/preview-iso
As the current version of UNetbootin obviously is missing the required “show all drives”-feature to copy to a user-selected partition you need to download the older Version 494 from http://sourceforge.net/projects/unetbootin/files/UNetbootin/494/unetbootin-linux-494/download
At first we need to create a NTFS partition on the drive. I used gparted for that. Find the current partition of your USB drive, unmount and remove it and create a new one with NTFS as the file system type. Remember the device name of your USB drive as stated in gparted. In my case it was “/dev/sdl1”.
Now mount the USB drive again. Mark the previously downloaded unetbootin as executable and start it.
Choose diskimage and find the downloaded Windows 10 ISO.
Then check “Show all drives” and select the device name from your USB drive. Press “OK” and we’re almost done.
Depending on the possible transfer speed the copy step will require some time to finish and will stay at 55% for quite some time. So don’t abort the copy process without waiting a little bit.