I don't have Windows Vista, but I am wondering if the registry is anything like XP with regard to where the details of the AutoPlay Handler descriptions, details, and commands are stored:
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\AutoplayHandlers]
in particular, the sub-key:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\AutoplayHandlers\EventHandlers
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\AutoplayHandlers\Handlers
Example:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\AutoplayHandlers\EventHandlers\MixedContentOnArrival
which on my system has the value "MSOpenFolder"
It would be particularly risky to start deleting keys and values in the registry, but if the registry of Vista is like XP, then I would assume that by deleting the actual values that specify the Handlers, then any user settings under:
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\AutoplayHandlers
wouldn't (or shouldn't) do anything.
Personally speaking, I think that messing with the registry this deeply would be asking for major trouble, and I won't even try testing this even though I am usually prepared to delve deeply for tweaks on a regular basis.