what is the term for proper nouns like Xerox that evolve into common use as in "will you please xerox this."

Answer 1

a neologism - specifically a "genericised trademark"

Answer 2

There are several related terms for words derived from proper names. The most common is the "eponymn", in which the name of a person is used to name of a particular place, tribe, discovery or other item.
http://en.wikipedia.org/wiki/Eponym
(includes links for lists of eponyms)
see also http://en.wikipedia.org/wiki/List_of_eponyms


The particular case you mention --in which a trademark or brand name becomes "THE colloquial description for a particular type of product or service as a result of widespread popular or cultural usage"-- is sometimes called a "genericized trademark"
http://en.wikipedia.org/wiki/Genericized_trademark#Former_trademarks_now_used_generically

here's a nice list of other examples:
http://en.wikipedia.org/wiki/List_of_generic_and_genericized_trademarks

Also, for the particular case of "Xerox" -- the name is actually taken from the coinage by the Haloid company of Rochester New York (later renamed "the Xerox Corporation") of the term "xerography" (= "dry writing") in place of the inventor's term ("electrophotography"). "XeroX" was part of their name for the first machine they developed using this process. The reason for the final "x" was so that the name would imitate the name of another Rochester company, "Kodak".
http://members.tripod.com/~earthdude1/xerox/index.html


(Reason for my special interest: My best friend's dad was part of the team that developed Xerox's COLOR copier.)

Answer 3

i don't think there is a single term for it, you could explain the process by saying the proprietary term has become the generic term (Band-Aid for bandage is another)

Answer 4

" Photocopy " will work.