XP pro command line problems! HELP!

I open the "DOS" window in xp Pro but I can't get it to change a directory to anythign other than what is under the C:\ Drive... How do I change this? I need to be able to access another drive say M:\ but the stupid thing won't let me even see it... let alone write anything to it.

Try "M:" and it should change to drive M. Dont use a \ after it.

well now it works after a windows repair