In Vista you can hold down shift and right-click and you will get the option to "Open Command Window Here." This will open a Command Prompt that is queued to your current directory.
Command prompt window will pop up:
Type in C: then hit return. At the cursor type in: ipconfig/flushdns or copy and past it to the right of the cursor. Hit enter. After it's cleared the dns you can close the command prompt window.