I am working on moving a .NET 1.1 App (Visual Studio.NET 2003) from Visual SourceSafe to Perforce Source Control. In Visual Studio.NET 2005 it is easy to change the source control provider by going to Tools -> Options -> Source Control -> Plug-in Selection. Unforunately in Visual Studio.NET 2003 it is not quite so straightforward and it isn’t possible to change the source control provider directly from the IDE. You need to modify the registry to actually change the source control provider in Visual Studio.NET 2003. I found a nice little application (Source Control Provider (SCP) Selector) that sits in your system tray that allows you to change the source control provider just by selecting the appropriate one from a list. It worked a charm for me!
Source Control Provider (SCP) Selector
Update: You will need to restart Visual Studio once you change your source control provider, it isn’t sufficient to just close and open the new solution.