Registry key location for software deployed via Group Policy?
Look in:
HKLM\Software\Microsoft\Windows\Current Version\Group Policy\AppMgmt. Find the key that corresponds to the software you're looking for, and delete it. Then run gpupdate /force and restart.
I believe:
GPO applied to the local computer:
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Group Policy\History
GPO applied to the currently logged on user:
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
\Group Policy\History