removing leo xp sp3

i have burned a copy of xp sp2 home edition on iso and tried rebooting the system so it would format the HD and then install from disc but it just loaded up my pc as usual. do i need to manually remove leo xp first?
Answer #1
Did you change the boot menu to cd rom so it will boot from disc first?
Answer #2
how do i do that?
Answer #3
found your problem when the computer starts, press F2 or F12, depends on your computer settings. You’ll see bootable sequences. Select “Boot From CDROM”. Restart your computer, and don’t forget to insert the disc
Answer #4
i tried pressing F2 and F12 but nothing happened
Answer #5
Can you give us the screenshot of your computer’s boot start?