PLEASE HELP! Major WinXP install problem

So I had Windows XP Home installed on my computer but the activation code I had for this disc was used to many times according to the activation screen. So I tried to install Windows XP Pro that I got. Well, the install seemed to be going fine up until it got to "Installing Devices" at which point the computer just kept restarting.

Finally I didn't know what to do so I hit the off button to restart it hoping it would get it unstuck from this loop. Now whenever I try to boot the computer from the XP CD it goes right to a screen that say "Retarting Windows Setup......." then proceeds to a black screen where it does nothing.

Need help bad.. can't figure out how to get out of this loop to retstart the setup.

Anyone???!