Git bash home directory different from Git extension than Git Bash
The git bash provided with msysgit in its repo is a script you can edit, in order to set HOME to %USERPROFILE%.
It is basically what it does by default, except if HOME is already defined, the git bash script won't modify that value (but you can, if you edit said script).
I suspect that, in your corporate environment, HOME is defined to a network drive, in order for various configuration files (maven, ssh, ...) to be stored on a remote, secure and backed-up drive.
That would explain why HOME is not changed by the Git bash script.
The Git Extension obviously isn't as careful as the first script, and will change/define whatever value it needs.
As the OP Steve B comments:
The HOME is set, for the Git bash, in etc/profile:
# Set up USER's home directoryif [ -z "$HOME" -o ! -d "$HOME" ]; then HOME="$HOMEDRIVE$HOMEPATH" if [ -z "$HOME" -o ! -d "$HOME" ]; then HOME="$USERPROFILE" fifiI removed the first candidate home location, and it works.