You're going to have to provide more detail than that. Did this ever work?
What version of Vista are you using? What have you tried? How is the
printer connected? Are you trying to scan from another machine (if yes,
this isn't possible). Etc.
I went to Dell's site and could only find an A960 printer so I'm not sure
this one is yours, but there are 32-bit drivers available for Vista. If you
didn't download the latest drivers/software for this printer from Dell's
website, do that. Maybe you neglected to install the scanning software for
all I know.