mount external drive on windows7 for git
Go to Disk Management in Computer Management, right-click the drive in question, click Change Drive Letters and Paths, and mount it to a folder in your C: drive.
Git Bash doesn't dynamically "mount" drives, so you need to close all Git Bash instances, then start a new instance. It should then appear under /g.
Source: http://comments.gmane.org/gmane.comp.version-control.msysgit/13133