It is very possible to do this. I am not saying I would do it myself but being a computer geek I am very interested in this theory.
Rich we never said cars run on xp lol . As jcb said software is software.
Everything on a computer down to the little icons on your desktop is made up of binary numbers which is a series of 1s and 0s eg. 110110001110110 all the data saved on an ecu is made up of 1s and 0s.
So to actually copy a remapped ecu you would need some type of custom made software that woul be able to read,copy and save the data of one cars ecu.
Then when connected to the car you want to transfer to the same software would have to be able to perhaps read the data on the ecu to be safe it should be able to backup and store the original data in case of errors. Then the software would be able to flash and rewrite the ecu data with the data taken from the ecu in car number 1,
The link madvw might be very close to what I am talking about.
Basically the software would be more of a simulator of an ecu writer.
To make it available to everyone it would be written for windows compatible computers and Macs too.
Sorry for the big techy speech but its a very interesting topic.
Edit: I did a few searches and found this so it seems it is available to do this and looks very very easy.
So JCB looks like we got to the botttom of this it can be done LOL
Find all the details here look down the page for instructions
http://ucables.com/ref/KWP2000
Supported audi cars as follows
Audi
A3 1.9 TDi VP37 Bosch EDC15V
A3 1.9 TDi VP37 Bosch EDC15VM
A3 1.9 TDi VP37 Bosch EDC15VM-1M
A4 1.9 TDi VP37 Bosch EDC15V
A4 1.9 TDi VP37 Bosch EDC15VM
A4 1.9 TDi VP37 Bosch EDC15VM-1M
A6 1.9 TDi PD Bosch EDC15P
A6 1.9 TDi VP37 Bosch EDC15V
A6 1.9 TDi VP37 Bosch EDC15VM
A6 1.9 TDi VP37 Bosch EDC15VM-1M
A2 1.4 TDi PD Bosch EDC15P
A3 1.9 TDi PD Bosch EDC15P
A4 1.9 TDi PD Bosch EDC15P
A4 2.5 TDi VP44 Bosch EDC15P
A6 2.5 TDi VP44 Bosch EDC15P
A8 2.5 TDi VP44 Bosch EDC15P
Allroad Quattro 2.5 TDi V6 Bosch EDC15P
A3 1.8T ME7.5
A4 1.8T ME7.5
A6 1.8T ME7.5
S3 1.8T ME7.5
TT 1.8T ME7.5
EDC15VM+
So i wonder if an A4 1.8T ME7.5 is what we have?