BIOS boot disk priority

I have a Dell XPS 410 running under Windows XP Media Center Edition.

I would like to configure BIOS so that I can set the order in which the computer, after being turned on, checks drives for files that will boot up the operating system.

What procedures, step by step and in detail, would I need to perform (from the very moment my computer is turned on) in order to modify the BIOS settings in this fashion (assuming that the computer we are dealing with is a Dell computer)?

Any and all help would be appreciated.