With windows you could use rawrite.exe, and from within linux dd would work.
dd if=/path/to/.img of=/dev/fd0 <-- obviously change for your situation.
Either way would work, net install or usb. Obviously a net install has its own big drawbacks, especially if your net connection is shoddy.
Hope it helps some
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PS. I have never made a bootable usb device so I may not be completely correct in the above, I have used dd in the above manner to take .img files and create driver disks, so apologies if I am way off base there.