I need to install FreeBSD 10 on an old PC with no CD drive but it has a USB port. I'm on a laptop running Windows 8.1 and have downloaded the FreeBSD 10 DVD ISO image. I have an external USB hard drive. I have the DVD ISO image. How do I go about preparing the external HDD with the files so that I can boot and install from this external HDD? I tried UNETBOOTIN from Windows but it does not recognize the external USB HDD.
How to install FreeBSD 10 from USB Hard drive?
freebsd;system installation
If your BIOS supports booting from USB, you can use one of the -memstick.img image files, located in the same area as where you got the .iso. file.  You can write that image directly to a USB stick using Win32 Disk Imager or similar, and then boot from it to install.