Just go ahead and install Windows 2000 on your second hard drive, and it will automatically creat an entry in your Windows boot file (Boot.ini, in the root of your C drive). If you want to manually change that file, boot into Windows XP, right click on My Computer, go to Properties, click on the Advanced tab, and at the bottom under Startup and Recovery, click Settings. Then, under System Startup, click Edit.
If you want to use another bootloader besides Microsoft's one, just do a search for operating system bootloader, or something along the lines of that.
I hope this is of some help to you.
-pSxMoD