Resetting the session in PowerShell
You can just dotsource your profile.
. $ProfileIf your profile handles errors when things like drives, or vars even exists, everything is ok.
You can try and dot-source your profile instead though some things may not work (like trying to redefine constants, etc).
A blog post to restart the shell:
http://scriptolog.blogspot.com/2006/12/restart-your-engins-powershell-way_28.html