How is the protiest kingdom different fromand similar to bacteria and viruses?
Protists and eukaryotic cells (that is, they have a membrane-enclosed nucleus that harbors the genetic material). Bacteria are prokaryotic cells (that is, they no not have a nucleus and thus the genetic material is in the cytoplasm). Viruses are not living cells because they are not able to reproduce on their own. They can only reproduce by infecting other cells and hijacking the cell's machinery to make more copies of itself. Thus, by definition, viruses are not cells because they can never replicate on their own.
Organisims in the proteist kingdom have distinct cellular structures, specifically a nucleus. Bacteria have no nucleus, and are essentially a self-replicating bag of DNA.
As near as I understood, viruses are not part of the standard taxonomic classification system, since they are neither living nor non-living. They have a classification system all their own:
Protists ARE NOT in a kingdom! just fyi. They are paraphlytic and are actually eukaryotes, unlike bacteria which are prokaryotes, lacking membrane bound organelles and a true nucleus. Viruses are not even considered to be living, but rather mobile pieces of genetic material.
Viruses (and some Bactria) are nonliving, while protists are very much alive. Also, refer to the link posted above ^.