The point is that you need to have both tetris tdf image and game image mounted, otherwise you have to keep the disc into the drive. It's a strange way to bypass copyprotections, similar to Ultima's works on Colin 2005 (so now don't accuse me of downloading games I've only read about it!!!
).
Seems in the future we'll not see no-cd\dvd crackz anymore, so better save money for a half-dozen drives to buy in the next 2 years
However, better to have tetris drivers running onto my pc than starforce (securom?) virus ones!!!