I just wanted to use two different source control providers on the same machine. I installed both clients but I discovered that the later installed is always the default. I searched the net all over for a tool, but no usable application was found. So I decided to write my own.
The solution is real simple and well described at: http://support.microsoft.com/default.aspx?scid=kb;en-us;319318.
Some registry settings and that's all.
Using the tool
Simply run the exe, choose the provider you want to be default, and click the button.
Only one provider can be active at a time. If you change the provider while another project is open it will lose the connection and continue working offline.
Hope you can use it.