Wiki: General availability October 25, 2001; 15 years ago.
General minimum recommended for XP was/is 512MB.
Microsoft specified minimum is 64MB, recommended 128MB. XP RTM with 128MB RAM was perfectly usable, obviously it was not a good idea to run lots of crap in background.
Nice... Didn't Google before posting... Busted. :)
You're the hopeful kind I see. XP was utter shit on "medium" hardware of its time. It ate ram like no tomorrow compared to 98.