I'm sorry, I wish I could. The only way I know is just from using it. The latest batch of new PC's we got had Windows XP/2000 dual installed on them. They were Pentium IV 1.5GHz, 256MB SDRAM, 16MB Nvidia Vanta, 20GB HDD, CD-ROM, Soundmax SC. I just set one up with Windows 2000 and the other with XP. Used them for about a 1/2 hour each and noticed the difference. I didn't run a benchmark test on them.
My machine at home is a Pentium III 866MHz, 512MB SDRAM, 64MB Nvidia Geforce 2 GTS, 20GB HDD DVD-ROM, SB Audigy SC. On that, I didn't really notice any difference in speed (except for starup and shutdown, which were faster) when I upgraded to Windows XP from 2000.
I'm sorry if it's not a professional way of testing things but it didn't really occur to me to benchmark it.