Black screen, no desktop, bios not accessible

My 3-year old Vaio running XP first gave a black screen a month ago but I was still able to see everything and use the computer with an external monitor. But today when I booted, I got only the initial Sony logo screen on the monitor (no complete boot to Windows XP). The only thing I was able to see was the Task Manager through Ctrl+Alt+Delete. I could see that most of the system files, including explorer, were running but still had no user desktop. I think either the OS is corrupted or the Bios is not working (in addition to the graphics card).

I tried rebooting with a bootable XP CD made when the computer was new, didn't work. Tried the Sony recovery CD, didn't work. Tried entering bios with F1, F2 and F3. No go. Tried Sony's automatic recovery, F10. Nothing. Tried disconnecting power & battery, holding down power key for 1 minute, then reconnecting power. Nothing. The keyboard commands don't seem to be working now either. I no longer even see the Sony logo on the monitor, there is no image now.

Shall I just throw it in the trash or is there still something else to try?