hi guy i ju bought a 2nd hand time pc problem it switches on then off and there,s a weird beepin sound which lasts until i switch it off at the mains any ideas would be grateful????

Count the number of beeps the computer makes, also listen for whether the beeps are long or short. That is the motherboard telling you there is something wrong with the machine, and the beeps are the description of the problem.

Just in case, open the machine, and check that the GFX and memory cards are properly seated - it may be moving the machine upset the insides.