I am looking for a regularly updated boot disk to cleanup viruses,
spyware & temporary files in all user profiles with little or no user
intervention. It should be based on a Linux/Unix type OS or perhaps a
BartPE type distro.

My preference is that the AV be CLAMAV or F-Prot

In regards to temporary files, something that incorporates an
automated ccleaner (see http://ccleaner.com ) will get the job done.

Regarding spyware, I'm not aware of a Linux based spyware remover, a
BartPE solution would likely incorporate Spybot &/or Adaware.

An ideal answer will provide the location of the site that provides
regularly updated boot disk ISOs & instructions for making same. In
other words, I'm happy downloading a pre-built ISO (if it does what I
need done, I'm willing to pay $20 per prebuilt ISO), but would like to
know how to roll my own when the ISO maintainer decides to get out of
the ISO maintenance business.