Exe files cannot be read as normal files. These are basically compiled files. You need special tools to decompile it and then read these files
I think you need something more than just seeing the contents of the EXE file using a HEX editor. Exe files are coming in different formats. Most of these formats are OS specific and supported by many popular decompilers. (However it is not a easy task to jump within assembly code). My favourite to do this is PE Explorer. Did that make any sense?
Yuo can find an article about EXE format in MSDOS and Windows operating systems at http://www.expertcore.org/viewtopic.php?f=48&t=1068
What exactly you are looking for ? You can read an EXE file in almost any language but the contents will not be human readable ( chipped, etc. ) anyway.
It seems you are trying to crack the EXE. If this is the case, it is illegal. But if you are so sure that it is not, then you must be familiar with EXE structure, machine code (assembly language) and use a program like PE explorer to edit in disassembly mode.