Decompiling Exes
 

Is there any way I can decompile exes to give me its parts? I'd like to change the some values in the exe and I can do it with a hex editor but thats fairly limited. The exe is not encrypted, obviously.

Did you Google it?

You're going to have about as much luck as you will if you run your car through a wringer and expect the original blueprints to pop out.

If you google for "decompiler" or "disassembler" you will find all sorts of entries.

Generally, decompilers will often be disassemblers: they allow you to get back to assembler code. The catch (apart from the fact you need to know the form of assembler emitted by the decompiler and have an assembler that will accept it) is that the output of the decompiler, like the format of executable files, is machine dependent and also very low level. Depending on the machine, the disassembly may not be complete.

I've heard some mention of programs that can decompile back to a higher level language (C, C++, etc) but nothing in common usage. As executable file formats (often) do not contain information such as variable names, type names, function names, etc (such info is often stripped by optimising compilers and linkers), the code that could be produced would be pretty basic (eg no higher level constructs, no use of the standard library) and arguably just as difficult to read as assembler code.

It would be easier all round to contact the author of the program and ask them to make the change. Even if they want to charge you a lot of money for the privilege.

If you want to disassemble to see the asm code of it, you can use w32dasm:

If you want to see and change the resourses of an executable you can use Resource Hacker:

Hope it's not for a bad thing! :D

I just want to change some of the values that are hardcoded. Most of the games files are in an archive, but some are in the exe. I've tried a disassembler before, but I couldn't understand the output very well. It was IDA pro. I'm making a mod for the game and want to improve it.

That's the cost. If you want to disassemble a program, you need to be able to understand the output to make use of it.
In that case, contact the author and either suggest an improvement or ask for source code.

Unfortunately, I don't really believe you: the most common reason I've observed for people trying to tweak an executable is to get around something the author has put in deliberately (eg checks of registration codes to enable features).

Unfortunately, the authors don't exist anymore - www.clevers.com is down. I want to be able to change the default damage a weapon has on someone, but it is just this one which is hardcoded, and change some other parameters. With a hex editor I could change the default port the game uses, I simply replaced 68 65 ea 00 00 with 68 67 ea 00 00.

Is it possible then to pay someone to do the work for me? Any suggestions?

Instead of changing the executable which may be checked to see if the executable is corrupt, you could also modify the values which gets sent to the network. So a packet sniffer with a filter, that would change certain values could help. I've read that somewhere. I don't know how or how it would work.

Although this has to do with Java, it's on the same train of thought. Can Java classes be decompiled to Java source files? I see decompilers (not that I will ever trust underhand programs) and wonder how a program's security can be maintained. As DaWei and grumpy said, the code will not be there in its entirety or "understandable" unless certain conditions are met. Is that the same for Java though? Private classes and methods are used to protect and hide code, but if it's reverse compiled, and it's done to a understandable/readable point, couldn't the security be traced and "gutted" or bypassed? If that's the case, how can security of a program be maintained?