CAN'T BOOT COMPUTER

I SETUP A DELL OPTIPLEX GX270, AND HOOKED UP TWO LABEL MAKERS (BRADY 6441, PRODIGY MAX 300). WHEN BOOTING, THE MACHINE EMITS ONE CONTINUOS BEEP (3SECS?), AND LOCKS UP AT W2K "STARTING UP" SCREEN. WHEN I TRIED TO BOOT IN SAFE MODE, THE BLUE SCREEN APPEARED W/THE FOLLOWING MSG: "**ADDRESS 8042DE20 BASE AT 80400000, DATESTAMP 3EE6C002 - NTOSKRNL.EXE, ALONG W/A FEW SUGGESTIONS ON REPAIR. AS SUGGESTED, I UNHOOKED THE LABEL MAKERS AND ATTEMPTED TO REBOOT. THOUGH THE BEEP IS GONE, THE MACHINE IS STILL STUCK AT THE W2K SCREEN