Sure, you can use virtually any data backend you want for the DSP as long as
you override the appropriate querying method(s). For Vista, search is going
to be in one of the internal APIs. Last I heard, Vista is using the
Indexing Service that's always been built into NT ("always" meaning as far
back as I remember; not necessarily back to 3.1) for its searching since
WinFS got pushed over to the SQL Server team, which is a shame because then
your Vista search API would just be another W*F. As it stands, I *think*
you can just treat the Indexing Service as a database, creating a
connectionstring for it and sending it SQL. See if this might help:
http://www.codeproject.com/aspnet/search.asp