My current PC is about a year old, 120 GHZ, 480 MB Ram
is this considered o.k or is it too slow?
Eh. If you are patient no prob.
There have been many breakthroughs in the last year. Particularly dual core processors. Also of note are much faster bus speeds and memory speeds. Additionally the hard drives today are usually 7200 rpm or faster.
I recommend the fastest Intel Core Duo you can afford equipped with 2Gb ram AT LEAST. HDD should be around 300-500Gb.
You can nurse that ol' system for a bit longer. Considering that speeds will increase and prices will fall perhaps you should, but with the advent of Verizon's new FIOS the web is about to get really really fast.
Of course this will only matter to you if you have the horsepower to keep up.