Both my office and home computers have Git Bash for Windows from the very same source (Git for Windows, that came with TortoiseGit), but Git Bash\'s prompt differs on both m
I would make a comment if I would have enough reputation,
but my guess is that the bashrc is not in your homefolder: ~/ but in the all users or general user folder(I dont know how it is named exactly). Look under your users where all users are located and search for .bashrc.
Look here : C:\Users\All Users or: C:\Users\Default User