I have been using an Olympus Transcription machine but today it wont work. It will work in FF and Rewind but not in listening mode. I cannot get any sound.

I saw the AS2400 is compatible with Windows XP/2000/Vista.

You can install Windows XP in your computer (I presume you have a 4th Gen Intel processor installed in it) and run this software under Windows XP.
On the Windows 8.1 Help and Support, search: Windows XP

For all information about dictation and transcription please visit www.dictaphones.com, alternatively simply ring Speak-IT on (0121) 456800. Their team of specialised staff with over 30 years of experience in both dictation and transcription will be more than happy to assist!

take it back for a warranty refund and get a different machine

Try clicking on Tools, then set auto backspace.

it is digital and does not have auto-rewind.

this should work:
http://www.olympusamerica.com/files/oima_cckb/AS-2400_Instructions_EN.pdf

Usually this means there is no sound card set up on the pc.

The answer is all in the serial number you use to install the DSS player!

Look carefully and you will see the recorder disk has in my case an [E] printed above the install serial number and the transcription pedal has [T]

Install the same disk with the E the driver is there, the control in Control Panel is there, but the foot switch does not work with the software. Put in the serial number with the [T] and foot switch works first time!

If you uninstall the play and then reinstall with the [T] serial number you do not need to reboot or even unplug the foot switch from the USB.

Bingo