Good day,

i using two operating system - windows xp and fedora core 3

with the boot loader --> gnome

Q1. how can i extend the countdown time when appear at gnome
boot loader which let me choose the optional OS.
What is the command?

Q2. Currently my default boot is fedora core 3, how can i
change the default boot to Window xp?


Please advice.

GNOME isn't a bootloader, it's a desktop environment. I think you mean GRUB. Really, you could have found the answers to your questions in the GRUB manual, but I'll answer them anyway. You need to edit your /boot/grub.conf or /boot/menu.lst to make the changes.

1. Look for the line that says "timeout x", where x is the number of seconds before booting the default entry. Change it to whatever you want.

2. Look for the line that says "default x", where x is the number of the entry that is the default (starting from 0, so the second entry would be 1). Change it to the relevant number.