If you want to extend the video/touchscreen breakout cable (the one that gives you your VGA plug), use a "9 Pin Mini-Din" cable. This may also be referred to as a 'bus mouse extension cable'. Don't confuse this with a normal PS/2 keyboard or mouse extension cable, they don't have enough pins and have a different shape inside.
Example cable:
http://www.computerplug.com/cable_mo...s-ext-tech.htm