Include_file_not_found error running classic ASP on IIS 8.5 - asp-classic

Question

I have a frustratingly simple problem. I've migrated a classic ASP site from a Windows Server 2003 IIS site to a shiny new 2012 R2 Server running IIS 8.5.
When I navigate to the home page (http://mydns/default.asp), I get a 500 error. The IIS logs show me this error:
GET /default.asp |4|ASP_0126|Include_file_not_found
Looking at the default.asp page, I see the following code at the top of the file:
<%# Language=VBScript %>
<!-- #include file="Include/common.asp" -->
<%
dim EMAIL_ID
if Request.QueryString = "" then
...
So, my assumption is that the error is being thrown due to the second line. In the website directory, the Include directory does exist, and there is a common.asp file inside of it.
# the default.asp page that I'm loading...
E:\websites\mywebsite>dir | findstr default
09/29/2015 10:30 AM 3,237 default.asp
# the common.asp page within the Include folder...
E:\websites\mywebsite>dir Include | findstr common
06/30/2015 10:27 AM 546 common.asp
Any idea why I would be getting an error about a file not found when I do see it in that directory?
Update 1: By navigating to the common.asp page in a browser, I get the following error in IIS:
GET /Include/common.asp |42|800a01ad|ActiveX_component_can't_create_object:_'Domain.clsAuth'
I found this article which helped me confirm that a DLL is missing so I am pursuing installing it on the new server.
Update 2: I was able to find the required Domain.dll on the old server. I used Dependency Walker to determine that Domain.dll depended on MSVBVM60.DLL so I grabbed both of these and moved them to the new server. I registered MSVBVM60.DLL successfully using C:\WINDOWS\system32>regsvr32.exe MSVBVM60.DLL, but registering Domain.dll failed. I got the following error message:
It turns out that this is the same error that you get if you try to register a file that doesn't exist. For instance, I tried to register "dummy.dll" and got the same error. It's like the system doesn't see the file. It autocompletes at the command line, but I can't register it. I also can't open it in Dependency Walker... the application says file not found. But I know it's there...
C:\WINDOWS\system32>dir | findstr Domain
04/27/2006 02:57 PM 24,576 Domain.dll
Update 3: The issue about registering the DLL was a 32 vs 64 bit thing. I had a 32 bit DLL in the system32 folder which is a 64 bit only folder. Once I moved it to the SysWOW64 folder (which is a 32 bit folder, go figure) I was able to register it. I also unregistered MSVBVM60.DLL from system32 and found that it was already available in SysWOW64.
So, this DLL issue is solved! But I'm getting the same error again due to a different include file. To be continued...
Update 4: The final include file error was indeed a missing include file.

Answer 1

Answering my own question... In my case, the issue was that the include file in question was throwing errors. I guess the fact that the ASP engine couldn't render the ASP include file resulted in the parent page throwing a "not found" error. By installing and registering a missing DLL, I was able to resolve my issue. Checkout the updates in the question for details.