Now this is handy: Geekbench, a cross-platform (Mac OS-X, Windows and Linux, that is) benchmark system. It’s written in platform-neutral C++.
My aging cobbled-together PC (1.7 Ghz Celeron) returns an overall score of 73.6.
Windows 2000 within Virtual PC on the above: 103.5 (I note it was only configured for 128Mb of “RAM”, even though Geekbench claims to need 256Mb.)
In all cases I shut down other applications, but obviously the figures would be subject to whatever background services were grabbing CPU time.