Minimum system for PC-based MP3 player

I'm considering building a PC-based MP3 player to retrofit into an old
Victrola cabinet I have. I will probably be running Winamp to actually
play the files. What I was wondering was how low on the food chain I can
go with processor and RAM without running into problems. I'm guessing that
a Pentium in the 100 - 200 MHz range should be OK as long as I'm running an
older OS like 98SE, but what if I want to run 2000? Can anybody recommend
the minimum system required to play MP3 reliably.

PS: I would probably also put a bare-bones FTP server on the box to
facilitate getting files onto the player from other computers on my
network, so please take this into account too. Thanks.