What video card do you have ? - some of them will make a continuous beep sound if the extra 6-pin or 8-pin power connector comes loose - (the card still gets enough power from the PCI-e slot to run in 2d mode but will emit the beep to let you know it can not get enough power to run in 3d mode) - so check the connectors on the video card !
I have a GeForce 7300 256Mb, I have checked all of my connectors and reseated the board, but I also have an on-board video source. I will remove my GeForce and plug into the on-board. I can't do that until tomorrow. That sounds like a possibility and will try it. From what I been reading it could be the Power Supply or the MB (PCHell.com). It was an expensive Itel MB, so the PS (which is a Thermatake 500w) is my next try. Thanks for the info, Bruce