Shoutbox

If you are using windows XP then this will work:
Go to Administrative Tools (normally in start>all programs>Administrative Tools)
And click "Computer Management"
Once that has loaded make sure the storage part of the tree-view is open, then click disk management.
You should then get this screen.

Right click on one of the drives where i've circled and a menu comes up with the option to "Change drive letter and paths"

Hope this helps