Do the following, reformat it on your Windows 7 machine.
Remove your SD card, also make sure RB is not running.
Click start, and type this in the search program and files: diskmgmt.msc
Maximize the window, notice the Disk you have in your window and put in your SD card, it will show up in that list also with a different name.
When it shows up, right click on it and select format. Follow the setup instruction after that.
Once formatted, remove it and plug it back in for the hell of it, once the computer notice it launch RB and see if its in there.