I have been able to get all my conversion errors taken care of. Let me detail out what I did (thanks to earlier posts in this thread - they helped shed a lot of light for me):
First things first, you want to take all the .vb and .cs files (NOT ascx.vb or aspx.vb, ONLY .vb and .cs) out of the source (NOT install) Events project, and put them into the app_code directory in your web project (a working dnn 4.2.5 site). Create an Events subdirectory, and an EventsWebControls subdirectory. You want two because one is written in C# and the other in VB, you cannot mix the two. These files are:
DataProvider.vb, EventBase.vb, EventController.vb, EventInfo.vb, SqlDataProvider.vb, AssemblyInfo.vb, EventNotification.vb
and
AssemblyInfo.cs, ColorCollection.cs, ColorItemHelper.cs, ColorUtility.cs, DNNCalendar.cs, DNNColorDropDown.cs, DNNColorDropDownBuilder.cs, DNNColorDropDownDesigner.cs, DNNColorDropDownEventArgs.cs, DNNColorDropDownException.cs, DotNetNuke.Events.WebControls.xml, Enums.cs
Now you have to modify your web.config file to have these two extra codeSubdirecties - you'll find one already in there, so just copy, paste, and modify to have the two new subdirectories
I followed the instructions found in the Module Upgrade Wizard. I manually did the find and replace instead of using the wizard.
After being done with these instructions, I fixed a warning about an obselete class: simply copy the obselete attribute syntax from the base class and insert it over the DotNetNuke class declaration that VS2005 is complaining about.
There is a page ( I forget which one, just look in your build warnings ) that complains about using the old AppSettings syntax. Fix to be .NET 2.0 compliant
One thing that the Module Upgrade Wizard does not mention is the need to delete the AssemblyName="DotNetNuke.Events.WebControls" out of the @Register syntax found at the top of your ascx pages (this is IF you are using the app_code directory and not pre-compiled dlls). If you do not delete the assembly reference, then the code in your App_Code directory will not be used, it will still be looking to the bin folder for the assemblies.
Once you do all that, you will need to make some changes to the code. I have posted here:
http://www.dotnetnuke.com/Community/ForumsDotNetNuke/tabid/795/mid/2108/threadid/19225/threadpage/2/scope/posts/Default.aspx#81131 instructions on how to do that.
Feel free to send me an email if you encounter errors or omissions here, I may have forgotten a step or something - but I think i've gotten it all...