Hi Plastic Nev, the PC belongs to my disabled friend, he asked me to have a look when it stopped powering on, i had a look at it and disconnected the 24pin on the mother board and replaced it, the green power light and the HDD light would light up for a few seconds before going out, the fan didn't seem to be working on the PSU so i bought a replacement and fitted it, the motherboard has a soild red light on it, not sure about if it has a speaker fitting or not but there is a black and red cable with speaker on the connector and i have connected it to the correct place on the motherboard but n have heard no beeps in any form, as for the PSU blowing up before i got to look at it my friend could comfirm this, if i knew what the flashing green light called LED_1 was for then i might have a clue as to were the problem lies
But thanks very much for your help and advice so far