Do Di
In 1986 he bought his first Atari ST and then wrote disassemblers and C-decompilers for several compilers and systems (TOS, UH-Pearl, Amiga DOS and HPUX). The decompilers all worked well, also for the GFA Basic on the ST. But he never released these programs, because he detest software piracy.
In 1994 he found that MS had put the sources into the executables compiled with VB3, and because MS didn't respond to his questions, he decided to publish a simple decompiler to make this fact known to every programmer. This resulted in the VBDis3 decompiler.
He has apparently completed decompilers for VB4 and VB5, but these are nowhere near as complete (in the decompilation sense) as the one for VB3. The VB4 decompiler (trial version, presumably) was available from decompiler.com software listings page. For users that have genuinely lost their source code, and can prove ownership, he will attempt a manual decompilation for a flat fee of US$100.
He had plans for a general decompiler for Windows executables, written with C/C++, that also would decompile at least those nasty setup programs. Some years ago he wrote the WinDis disassembler for Windows programs which is pretty good, but the next step including a database for the system calls and data structures of Windows is not yet completed. He is supposed to have written a 68K decompiler, but I have not seen it.