Make old exe files compatible with Windows 2012R2

Hello, We have several executable files that were developed among 2003-2004 with C++, in Microsoft Visual Studio 6.0. Neither the developers nor the source code is available by now. Till now, these programs have been run on a Windows 2003 Server environment, as windows services. Now we would like to upgrade our Windows, thus we need these programs to run on Windows Server 2012R2 as well. To test, we defined a server for one of those executables and tried to start it. We get an error "Error 1053: The service did not respond to the start or control request in a timely fashion." We have the information this exe was written using .NET 1.1 framework, so we suspect the above error occurs because Windows Server 2012R2 does not support .NET 1.1 framework. We tried to decompile the exe with Reflector and ILDASM but they could not be decompiled as we get "[login to view URL] has no valid CLR header and cannot be disassembled." error. It looks like the exe files are not managed type. We need an expert to find a way making these programs work in Windows 2012 R2 environment. I don't know if it would be possible to "upgrade" the .NET framework the exe files use without decompiling it. Or any other alternative approach is also welcome as long as it gets working. We will see if a practical solution can be provided by an expert here. Hence the budget. Otherwise we might eventually decide not to stick with the current programs and start developing totally in-house. Thanks.