I have just been giving a home built pc and it was working when i got it, now since i got it home and turned it on it starts to load up then shuts itself off and there is a beeping noice coming from it. can anyone help?

how many beeps do you get?

Continuous beeps but sounds more like a siren and it continues unless i unplug the power

is it beeping before you turn the PC on, as soon as it's plugged into the mains?

have you checked to see if anything is loose?

No it doesnt beep b4 i turn it on, when i do turn it on it starts to boot up the the siren sounding beeps starts and it turns itself off

can you check all the connections inside the unit, if it was working before you moved it something may be loose

"... but sounds more like a siren ..."

Some motherboards emit a siren type sound (as opposed to beeps) when there's a CPU overheat problem. Hence the immediate shutdown. Ensure that the cpu heatsink is in good contact with the CPU, and that the CPU fan is indeed running, and the heatsink/fan aren't clogged with dust.