Motherboard, RAM or CPU

My screen displayed a strange orange and pink fine checkerboard/herringbone pattern today. The display then lost it's feed as if the pc had been turned off but all case fans etc were still running. I pressed the power button and the pc turned off immediately. I powered up again and the POST started with a beep as normal, followed by another indicating a RAM issue. I took one 1Mb RAM stick out and tried again but still with the RAM beep. I swapped the RAM over for the other stick and nothing, not even a POST. I put the original RAM in and tried again but still the same, no POST. I've swapped the graphics card for another but still the same problem. I had what I thought was a RAM problem (1 beep) around three weeks ago and got the RAM swapped as it was only 6 months old - the problem seemingly cured but now it's reared its ugly head again.

Could the CPU or mobo be the problem and if so, how likely? I must admit, I'm leaning towards the CPU because for a P4 it has seemed very lethargic for the last six months or so, with many fairly easy tasks for it taking ages to complete.

Mobo - MSI 848P NEO-V
CPU - Intel P4 3GHz Northwood Socket 478
Graphics -ATI Radeon X1600
OS - Vista Home Prem.

Thanks in advance.

Try using a different monitor, its possible that your monitor has given out, post back after you try.

!OP