previous vs old

previous is not a noun while old is a noun.

Word	Noun	Adjective	Verb	Adverb
previous	No	Yes	No	No
old	Yes	Yes	No	No

As adjectives, previous and old are synonyms defined as:

previous (noun)	old (noun)
	past times

previous (adjective)	old (adjective)
too soon or too hasty	of long duration; not new
(used especially of persons) of the immediate past	(used especially of persons) having lived for a relatively long time or attained a specific age
just preceding something else in time or order	skilled through long experience
	(used for emphasis) very familiar
	excellent
	just preceding something else in time or order
	belonging to some prior time