>Even back in 2001 when Windows XP was released it was "common knowledge" that the practical minimum requirement for Windows XP was 512 MB RAM
It really wasn't. I got my first summer job in 2001, and used the money to build a machine with 384MB of RAM, which everyone considered ludicrous. It was a couple of years after that before 512MB became at all commonplace (and indeed three or four years ago 512MB was *still* the default on machines marketed to everyday users).
The release version of Windows XP runs just fine with 128MB; SP3 is basically unusable without at least 512 (though I still see people using it with 256).