A problem concerd with my hp 520 laptop

Question

dear sir, my laptop is hp 520 with celeron m processor ,everything was working rightly but it used to get stuck up when i used to switch it on.....i had to switch it off and start it many times ....but yesterday same thing happened and now nothing is coming .i thought if i format my system it wud become proper again so i put the windows xp bootable cd it started but it is saying hard disk is not installed please help me sir