On other machines (a tower hp/Compaq/ubuntu, and a hp-laptop/win7) KolibriOS and FreeDos auto-boot from a USB stick without problem.
On an acer-packard-bell easynote TE69BM model "Z5WT3" laptop (win 8.1) I can't get KolibriOS nor FreeDos to work.
In the setup firmware, I can only choose "UEFI" mode.
Putting "USB HDD" on top of the priority order does not make a change.
The boot manager (F9) only displays "1. windows boot manager" in its boot options menu.
I fear that new computers may drop Bios compatibility, and a UEFI solution will have to be found.
I apologize for my ignorance about UEFI boot firmware and I hope that I don't post nonsense.
Congratulations with your work on Rufus.
From Wikipedia http://en.wikipedia.org/wiki/Unified_Extensible_Firmware_Interface
With the release of Windows 8 in October 2012, Microsoft's certification requirements now require that computers include firmware that implements the UEFI specification. Furthermore, if the computer supports the "Connected Standby" feature of Windows 8 (which allows devices to have power management comparable to smartphones, with an almost instantaneous return from standby mode), then the firmware is not permitted to contain a Compatibility Support Module (CSM).
As such, systems that support Connected Standby are incapable of booting Legacy BIOS operating systems