I am really interested in assembly language and I want to learn about how exe files work how dlls run etc... and I have an idea of writing an application to decompile an exe to assembly code since i am not a very good assembly programmer and with the lack of knowledge of the inner working of exe I couldn't do it. Since I can read an exe in hex i think it is not impossible but I don't know how to write my own program. Any resources or any help would be appreciated.
I think you're looking for a disassembler not a decompiler. IDA pro seems to be popular and you can download an older version for free at http://www.hex-rays.com/idapro/idadownfreeware.htm
There are a lot of dissemblers already written for you (see above), but I don't think reading disassembled code is going to help you become a better assembly writer. The main reason for this is that compilers do A LOT of optimization before they generate assemblies. Often this makes for very tricky code to read but highly efficient code to analyze.
Take a look at this Decompilation Wiki, I suspect it will answer most of your questions.
If you're interested in what a compiled program looks like at the a assembler level a much more meaningful approach would be compile and look at the generated assembly. For example with gcc/g++ this just requires gcc -c -S filename.c and will leave a clear text assembly file to look at.
来源：https://stackoverflow.com/questions/4565796/how-to-decompile-an-exe-or-a-dll-to-assembly