CentOS

hey, newbie here.
I have a x86 based system.
My password was sabatoged so I need to remove the partition without logging on. I can't use parted on the command line before booting. I tried booting from the installation cd, but it automatically boots from the hard disk. I don't know the device string of the usb cd drive I'm using.
How can I force the system to boot from the cd?

Welcome to CentOS.
Please do the new user reading:
http://www.centos.org/modules/newbb/viewforum.php?forum=47

Boot up single user, and use the passwd command to change the password.
Another option is to boot the DVD in rescue mode, chroot to your system and run passwd.

See [url=http://www.centos.org/docs/5/html/Installation_Guide-en-US/s1-rescuemode-booting-single.html]Booting into Single-User Mode[/url]

You'll select "CentOS release 5..." at GRUB menu.

I tried single user mode and change my password, and it said that it successfully changed. But when I tried to log in it still said login incorrect.
Sorry, my system is x83 I made a mistake. I've been trying to boot from the cd but it won't. I tried grub append>boot cd. I tried grub append>boot cd rescue mode. But it always booted from the harddisk. The cd I'm using is CentOS 5.3 cd #1. What's the exact append command I should use to force boot from the cd.

Not a CentOS or GRUB problem. You need to set your BIOS boot order to boot from the CD device before the hard disk.