One long beep is (usually) a memory error.
Could be anything from a bad contact with the mobo, to memory on its way out.
Try reseating the RAM in the motherboard, see if that helps
I finally removed the mb from the case disconnected all connections except 12 & 24 pin power, cpu fan and power switch. One memory strip and now whn I apply power, there is a constream of short beeps. Any suggestions??