Yup, welcome.
The game is really heavy on the processor AND the graphics card.
I'm on a "tweaked" Geforce 3 and a P4 (1500) "tweaked again".
Even the OS makes a difference. I'm on 98SE and swear it's the best but other guys who've been here a while might differ slightly.
Most of us get it between 90 and 99% of the way there but nobody's ever managed to run it "perfectly". There's also a wealth of high quality add-ons to keep it up to date.
Give it a bash, come back here to find out what you need to do next.
Like I said, WELCOME! - (evil laugh).
....................I quite like this now.