I've worked it out with the help of all of the above suggestions, I renamed the PendingFIleRenameOperations and checked the run and runonce (nothing other than VMtools), no msiexec running.
Rebooted server and had the same issue and the PendingFIleRenameOperations had returned. So I checked the .dll that was listed in this key and found it related to a lexmark printer!!! I disabled the "print spooler" as it isn't required on the server anyway, rebooted and can open SIM.
Thanks, Cat