Supaplex

[Qbix]

I've always been a fan of this game.
you can find a free download of it here
http://www.elmerproductions.com/sp/

The legal states of the game might be a bit tricky. I know that site has permission to distribute it.
I found the unmodified version of the game as well. but it requires codes to operate.

[ThreeHeadedMonkey]

Excellent game, well worth checking out for puzzle fans! I've also bought a copy of Igor: The Time Machine (a Supaplex remake by fans - also available from that site) a few years ago. It's quite enjoyable for those who have beaten Supaplex and are looking for a new challenge.