The only good solution is to port the oldest code (2006) to VS2010 (or both project to newer compilers), and compile a new executable from a fresh solution where you combine both projects as you wish.
As commented, merging two executables makes little sense in general (what is the entry point ? What about conflicting symbols ? What about the fact that different compilers and linkers generated those binaries ? etc…)
solved Combining two exe files [closed]