Certainly Dave. I did that already on my PC since more than a year. And, it's not complicated at all to do it.
All what you have to do now is, to install the XP on the second drive (attentiion: It must be on the slave drive, not the master). That means that you can leave your ME as it is (on the master).
While you start the installation of XP, take the option which tells that you "want to choose the installation partion and drive by yourself" , (not default, and not automatical installation).
Later, everytime, it reboots by giving you automatically both options of what OS you want to boot. Then you can choose the one which you want. During about 30 seconds, If you don't select one of them to boot, it'll boot from the master drive, "Windows ME" (in your case) by default.