TFS - "the server folder is not mapped" followed by "path already mapped in workspace"

I am using a machine that was set up for me by someone else. I already have the code for various projects/solutions locally. When I try from Source Control Explorer to "Get latest version" it tells me "the server folder is not mapped". Fair enough, I use the dialog to try to map it - and get "path already mapped in workspace" It's driving me nuts - I hope it is something simple! I have not got server access, if that matters.