A realllly bad registry key which was actually discovered by EVDirector is :
There are very few references to it on the Microsoft Support site, but here is one good link.
What this registry key does, if set to a non-zero value, is to attempt to clear up deleted data in both PST files and OST files when Outlook closes. This of course is bad.. as it leaves Outlook open (shutting down) for an extended period. This is especially true if you consider :-
* A large .OST file
* A large Virtual Vault .MDC file, or files.
* A large number of Vault Cache .DB files
You can imagine that it might take a considerable length of time to shutdown = bad. I’m not sure why anyone would want this functionality – I guess it’s for those sorts of environments where delete means ‘really, really, really delete’.