Thanks for the post, it was useful for me. But I used an alternative that I think it is easier. It requires just a usb stick.

1 - Download unetbootin:
'sudo apt-get install unetbootin' or direct from www.unetbootin.sourceforge.net

2 - Start the application. Select FreeDos as distribution in the main dialog. Your USB stick will probably be already selected in the lower dialog, if not, do it (remeber to format it first as FAT).

3 - The application will automatically download and install the odin version of freedos(just 1,4MB!). It will also make your usb bootable.

4 - Copy the wdidle3.exe to the usb stick.

5 - Reboot the system with the usb stick as first boot alternative. When asked select the live CD version of freeDOS.

6 - In the prompt type c:, so that you get to the root of the usb stick. Then type as usual wdidle3 /S255 and that's it!