XP Won’t Restart

Just out of the blue, my XP Prof. workstation (P4, 1.6 Gb Mhz, 40 Gb HDD)seems to have lost its ability to restart. It will log off and shut down properly, but when I need to do a restart, the screen appears to be doing its thing initially, but then goes black, the unit beeps a couple of times, and both the power and disk activity lights remain on. The only recourse to get it back in motion is to hit the power or reset button (gag!). Can anyone suggest something I might try to get old XP back to normal?

Thanks.