If you want to access a dos command prompt in Windows Vista in a specific directory you can now shift click on a directory in windows explorer. See this article – http://blogs.msdn.com/tims/archive/2006/09/18/windows-vista-secret-1-open-command-prompt-here.aspx
I have found this to not work well – better to use this old program which works well in windows vista called dos here. Just download the file dos here file download
open the zip file and right click to install the .inf which will add a right click window option for windows vista ..