I can only think of one app right off the top of my head that might work, and it's free, so it is at least worth a shot...http://www.pcinspector.de/file_recovery/UK/welcome.htm
It is fairly intuitive to use, and if not, the instructions are fairly clear....I have used it a few times to recover 'deleted' files, but I have never used it in an instance such as the one you face. It claims it will work even if the FAT table is erased (which I suspect may be the case here)
To answer your question about the error message, Hard Drive Mechanic has a fairly extensive help page. Your exact question is handled here:
An XMS driver is a file that handles how the memory in the computer is addressed by programs run on it. Usually this file is on your boot disk. Try re-starting your PC from a boot disk without Config.sys or Himem.sys
Help page is here:http://www.pcrecovery.com/product.asp?Prod...foTypeID=5#q013
Here is a link that will help you create a boot disk, but it means that you will also need to be able to navigate from a command line interface. I can probably help you get there though.
Here is a link for creating boot disks specific to your system:http://www.mirrors.org/archived_software/w...om/original.htm
Or you can create your own.by using the instructions here:http://www.computerhope.com/boot.htm#05
If all of that fails, don't give up hope quite yet. It is possible that the files can yet be recovered using a bootable linux disk (specifically one called Knoppix). It may sound intimidating, but it isn't too bad.
Let me know if I can be of more help.