How powerful a machine do I need to support a site of the following characteristics?

- 30GB bandwidth per month
- 150,000+ visits
- 1,200,000 page impressions
- Windows 2000

Sensible CPU / RAM specs are what I'm after.

You really would not need anything too extravagant to support that number of requests -- assuming they are not all coming at the same time during the month :).

Any Pentium III server with 256+ Megs of RAM should support that configuration fine.

As he is asking for W2K server I would suggest far more RAM, at least 512 MB.