Ok Thanks you all so far.
Now for WILL's answer...

My main problem seems to be that DelphiX (which I am going to try for a while. It seems the best way to start of...) uses this TPicture in it's TDXImageList. How do I get the TBitmap32 in there without assigning (which means moving too much memory around)?

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There is a lemmingsgame in higher resolution, written in java. It's called Lemmini (http://lemmini.de/).
And also WinLemmings has higher resolution, but unfortunately this is not a very good remake in my opinion (bugs, sluggy mouse reaction, worse game-mechanics). Lemmini is better.

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As for the music and sounds in my remake: the musics are mod-files from the amiga version (it seems impossible to hack adlib.dat, which contains soundblaster emulation data I think) . The sounds I borrowed from the winlemmings version. Sounds will change a bit. That's still in progress. I think I am going to use the amiga sounds as well.
So the "cloning" of sounds is not 100% possible I think.