Windows XP Hangs

I have installed windows XP Pro to a new computer that is 1700+ AMD chip and match board. XP for some reason hangs on bootup or after signing in and/or even went doing down loads. The only thing that I have not do is install the services pack which is on order (because I can not download it). It Hangs up so bad that sometimes I have to turn the unit off for about 1/2 hour before it will reboot with out locking up.