How to decompile the vb6 executable file(exe)?

Question

I am given a list of old exe files where the original source code are lost.

While i am able to extract code from some of the exe files using tools like DotPeek or ILSpy or JustDecompile.

I see a couple of them failed to decompile. I am getting the below similar error

What would be the next step I need to do to extract code or do reverse engineer?

kindly let me know.

what kind of assembly are they? are they .net ones or something else? — Daniel A. White, Nov 23 '22 at 21:00
Its hard to tell but I am seeing MZ at the beginning if I open the exe in notepad. — simpleorchid, Nov 23 '22 at 22:28
Are you ONLY asking about VB6 or are you asking about multiple different technologies? — StayOnTarget, Nov 28 '22 at 13:08
Does this answer your question? [Is there a Visual Basic 6 decompiler?](https://stackoverflow.com/questions/414068/is-there-a-visual-basic-6-decompiler) — StayOnTarget, Nov 28 '22 at 13:08
I see those exe files made around 2015. so cant confirm which technologies are used. but I believe all exe files are compiled using microsoft related coding. kindly advise. — simpleorchid, Apr 26 '23 at 17:05

score 0 · Answer 1 · answered Nov 24 '22 at 00:47

If there is no CLR header then it is probably not a .NET application and you would have to go deeper.

Start with something like PEiD, it should hopefully tell you if it is packed and basic guessing of the compiler used. If it is VB6 or Delphi you might want to look for specific de-compilers for those, otherwise go back to basic disassembly.

Both IDA and Ghidra can be used for free...

score 0 · Answer 2 · answered Nov 24 '22 at 08:59

Here's a tool that automatically tries to identify a file. It takes an "educated guess" based on similar files analyzed and community contributed identifications (I contributed some definitions). For executables, it tries to name the programming language/compiler, too: TrID. If the file is too large for the online analyzer, there's a link to download a (Windows) standalone version. (Disclaimer:) I know Marco as a regular and knowledgeable contributor from a programming forum where this project started. It has been featured in a Computer Forensic article by the renowned German computer magazine c't.

How to decompile the vb6 executable file(exe)?

2 Answers2