to 'sign' the assembly with a 'strong name.
You only need to do this if you are going to place the assembly in the GAC. I do not recommend doing this if you are going to make the DLL COM-Enabled. To make your assembly properly accessible via VB6, you may need to create a TLB and update the registry. You cannot self register a .NET DLL like you could in previous languages. You will need to call the REGASM tool from the Visual Studio 2005 Command Prompt. This will create your TLB and register the assembly.
During the installation you can manually add the keys to the registry to make the COM visible on the workstation.
REGASM
regasm "c:\My Assembly Folder\MyAssembly.dll" /tlb:"c:\My Output Folder\MyAssembly.tlb"
FYI, to sign your assembly for strong-typing so it can be added to the GAC, just right-click on the project and go to the project properties. Select the Signing tab. Place a check mar in the "Sign the assembly" check box and create a new pfx file. Rebuild the assembly and you will then be able to add it to the GAC.