I'm (still) getting the question about how to use TFS from VS 2003 and other Visual Source Safe compatible environments so I thought I'd summarize what's required in this post. In short we use a provider for TFS that implements the old Visual Source Safe API (MSSCCI). When used, the environment that uses the MSSCCI provider can use TFS instead. The integration is quite seamless but when you need to switch between environments (TFS to VSS) then the Windows Registry is used and there's no integrated support for changing between the different providers. To do so you'll use one of the tools at the bottom of the post.
The MSSCCI provider for TFS can be downloaded from here.
Ed Hintz (MSFT) has a good post on how to the integration works here.
Finally Vertigo has written a good post on how to use the TFS integration in VS 2003.
Here are some handy utilities to swith between the different source control providers installed: