I think to enter this you click the F2 key.
To change Boot Sequence in your BIOS
Reboot the system and at the first post screen (where it is counting up memory) start tapping the Appropriate button
This will enter you into the Bios\Cmos area.
Find the Advanced area and click Enter
Look for Boot Sequence or Boot Options and highlight that click Enter
Now highlight the first drive and follow the directions on the bottom of the screen on how to modify it and change it to CDrom.
Change the second drive to the C or Main Drive
Once that is done then click F10 to Save and Exit
You will prompted to enter Y to verify Save and Exit. Click Y and the system will now reboot with the new settings.
Hopefully you have already put the XP cd in the drive before all this. If everything is setup correctly you will get a black screen with the following message in the upper left corner:
"Push Any Key To Boot To Cd". When you see this then push any key and the cd will take over. Then follow the prompts or if you need assistance we will help.