Interop error with earlier versions of Framework

I have a COM object that is referenced in my project. When I build the project with target framework 4.5 everything works. However if I change the target framework to 3.5 (or 2.0), the code throws an exception when trying to instantiate the class using DLLName.exe (I presume it is an ActiveX EXE)

The following is the error (I translated it from a foreign language so it may not be exact):

System.BadImageFormatException: Could not load file or assembly  'Interop.DLLname, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' or one of its dependencies.. This assembly is built by a runtime newer than the currently loaded runtime and cannot be loaded.
File name: 'Interop.DLLname, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'
....

Assembly loaded from:  C:\Windows\Microsoft.NET\Framework\v2.0.50727\mscorwks.dll
Running under file execution  C:\Users\Admin\Documents\Visual Studio 2012\Projects\....t\bin\Debug\EXEname.vshost.exe
#NAME?
=== Pre-bind state information ===
LOG: User = 
LOG: DisplayName = Interop.DLLname, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null
 (Fully-specified)
LOG: Appbase = file:///C:/Users/Admin/Documents/Visual Studio 2012/Projects/............/bin/Debug/
LOG: Initial PrivatePath = NULL
Assembly calls : EXEname, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null.
===
....
LOG: Using computer file configuration from C:\Windows\Microsoft.NET\Framework\v2.0.50727\config\machine.config.
....
ERR: Failed to complete assembly definition (hr = 0x8013101b). 

I have tried to remove interop.DLLname.dll from the bin/obj folders, I have checked that all the projects in the build are targeting Framework 2.0

Am I missing something else?

You are getting this error because the com wrapper dll (interop.DLLname.dll) was generated for .net 4.5, obviously it can not be used in earlier versions of .net due to the different CLR version. You need to get the wrapper for .net 2.0 and reference it. Here is link on how to generate a com wrapper http://msdn.microsoft.com/en-us/library/ms404285%28v=vs.80%29.aspx