I suppose following on from the discussion of installers.

What would the best way be to supply upgrades to people with
my products from my Web site?

I am thinking on the lines of the FBII upgrade installer.

All I want to do is check that they have an existing copy of
of the product on their machine, say with a creator type CWCR.
If so unpack and install, if not an appropriate message.

Can this all be done from a commercial installer or would I have to 
write it myself or has someone already done this that I could buy a copy
and customise?

Martin