How to decompile .exe files

You can't decompile it to C++ again. Though, you could disassemble it. Not sure if Dev C++ can do that, but I know Visual Studio can do it for sure.

"Yes, but none of them will manage to produce readable enough code to worth the effort. You will spend more time trying to read the decompiled source with assembler blocks inside, than rewriting your old app from scratch." (StackExchange post).

- http://www.hex-rays.com/products/ida/index.shtml

I used to use a version with a similar name (IDA or IDE strangely enough mirroring another acronym I swear) to decompile DOS executables.

Doing the same with a Win32 executable will be a pain in the arse and it would be faster to just re-write the code in a more modern OOP way (eg, using .NET and C#).