How do I reset my dell bios for my Dell dimension 2400

I was trying to start all over and reinstall windows for the provided CD and add a new hard drive but I end up messing around with the bios and now after my computer restarts after running the Dell Operating System CD it need to start over it just returns to running the same thing on the Dell Operating System CD.  If I remove the cd it ask me to press F1 to continue or F2 to enter bios setup. How can I reset my dell bios for my Dell dimension 2400, I think if I reset it everything will be back to normal.