The tlb file is required.  COM+ runs in unmanaged space, your .NET app in managed space.

.NET libraries are a replacement for COM but not COM+ (now called .NET Enterprise Services).  COM+ basically is a set of runtime services.

Have a look at this for more:

http://msdn.microsoft.com/msdnmag/issues/01/10/complus/default.aspx

especially the section:

Deploying a Configured Class

 Hi Group,

 I have a question. I am deploying my VC++ App and it works well with App_Name.tlb File included. Else it gives me an error saying "Error: Loading DLL".  I really don't understand why .Net App requires .tlb file?

 U folks have any idea?

 TIA
 Sachin