First of all check the VSS service, which ACCOUNT is used to start it? It should be NETWORK SERVICE.
Second, run this command:
C:\Program Files\Common Files\Microsoft Shared\web server extensions\12\bin\stsadm.exe -o registerwsswriter
Finally, if the step above doesn't resolve your issue... you COULD delete that entry. Honestly the event id is a warning, so the process doesn't fail... anyway, if that entry is no longer used, you should be able to remove it. Maybe, export the entire registry first, then delete, then reboot, then verify :)