There's a pthreads library for Windows that works with MSVC, but it's not as fast. I would prefer something like OpenMP that's more flexible and has better support for Windows.
i'd strongly suggest you look into Qt - it's multi-platform, free and incredibly user-friendly
it has all the multi-threading and graphical features you'll need... i was thing of porting it myself, but if you wanna have a go at it, i won't stand in your way
well... i may give it another shot... let's see what i can come up with...