Windows 10 Installer issues

Im trying to create a windows 10 boot drive on a 128gb usb or 1tb external drive. I get to the creating windows media part at 30% and everytime it says not enough space. I have reformated both drives so there is more than enough space. What am i doing wrong?

Generally speaking, W10 and all other versions of Windows do not allow you to boot their OS from an external storage device (USB flash drive or USB HDD). There are some hacks that some people here have gotten to work that way; but it's not reliable in my opinion as well as not recommended. Linux versions such as Ubuntu and Mint do an outstanding job of running from USB external storage devices; and run in memory and you don't have to install the OS onto the boot drive if you don't wish to.

Best,
<<<BIGBEARJEDI>>>