Look for the Poser key under either of these two registry keys:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall
HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall
When you find the uninstall key for Poser, just delete it.
The key could also be a GUID (the long, alphanumeric strings), in which case you'll have to click the key and look at the DisplayName item in the right-side pane.