If Conitec have a Windows server, Conitec can develop a web service which can allow the .net Framework application to connect to the server. Written either in C# or VB.net, a webservice can talk to the database server like in SQL Server 2005, then in the client-side application (the updating program) can then give the version information to the server, which the web service can check the application's version with the version that's already in the server, then the web service will return whether the the 2 version numbers match. If it's true, then the user already have an up-to-date version of the software. If false, then start downloading the updates.

It doesn't take that much time to do this with C#/VB.net than unmanaged C++.