: I would like to link a SNES to a PC by the printer port to play the demo from the hard drive of my PC
: If anyone knews how to do ... I'm interested ..
I can't help much, since I'm not an hardware expert, but here goes some theorical explanation:
First of all, you'll need to know the SNES cartridge pinout (Search for it on some search engine), or find some cartridge that you can *destroy*
Second, you will have to replace the cartridge's ROM chip with a RAM or an EEPROM.
About the linking with the PC's parallel port, you will have to add some hardware on the cartridge that would read from the parallel port and then write the data in the RAM/EEPROM.