OPENROWSET with Microsoft.Jet.OLEDB.4.0

I came across this error when trying to alter a procedure containing an OPENROWSET with Microsoft.Jet.OLEDB.4.0 on SQL Server 2005:

alter procedure Cannot initialize the data source object of OLE DB provider "Microsoft.Jet.OLEDB.4.0" for linked server "(null)".

I was surprised to see this when just trying to alter a procedure.  I found the solution was to edit the following registry key value:

HKLM\SOFTWARE\Microsoft\Microsoft SQL Server\<Instance>\Providers\Microsoft.Jet.OLEDB.4.0\AllowInProcess to 0