That being said, the fix (other than RTFM) is to set the environment variable HOME manually in whatever way is most convenient (I find the advanced system properties method described here easiest). As you've discovered powershell does this for you within a powershell session, so you can take the value that it uses and set HOME to that so emacs uses the same directory. Don't forget to move your init files and change anything that assumes your emacs lives in appdata.