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.

Answer 1

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...

Answer 2

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.