If you weren't sure, then how can you say that the
dd method worked? Also, that ain't the way. You have to use Rufus to make the USB drive bootable;not that I discourage the dd practices, since it is Windows we are talking about, I believe it is best to use Rufus to handle this for you.
If you have a Windows installation already, then boot into it and follow the steps below or else, use virtualbox.
According to: http://www.cnet.com/how-to/how-to-install-windows-10-technical-preview-from-a-flash-drive/
you'll need at least 4GB flash drive (8GB for 64-bit).
--> Download and run Rufus, then insert your flash drive, making sure it doesn't contain any important data. (It's about to get wiped.) Rufus should automatically detect the drive and list it in the Device field. (If not, select the drive manually.)
--> Notice the check box marked, "Create a bootable disk using." Click the drive icon at the far right, then navigate to wherever you saved the Windows 10 ISO file. Select it, and then click Start. (All the other default settings in Rufus should be fine.)
--> This will take some time, perhaps as long as 20-30 minutes. Don't be alarmed (or confused) if an Explorer window appears for the flash drive; just leave it alone until Rufus reports "DONE." Then you can close the program and drive window and remove the drive.
--> Now it's time for the old PC. Plug the flash drive into a USB port, then power up the system. Most likely, it won't be configured to boot from an external drive by default, so you may need to jump into a startup menu or the BIOS during the POST. Ultimately, you need to force the machine to boot from the flash drive. Once you've done that, reboot, then follow the Windows installation instructions.
All the best!