No beeps sometimes

Initially when the problem started cpu gave no beep..however after a few attempts it booted well but after an hour monitor went blank with fans spinning..
After a day it sometimes gave no beep and if it did, monitor again went blank on xp loading screen..I somehow reinstalled win xp but problem continues..sometimes no beeps... sometimes boots up well but on opening the very first web page on any browser computer freezes and sometimes works fine...
specs:
p4 3.06 ghz
ram 1 gb
ati radeon xpress 200 integrated graphics
 
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