Toshiba Tecra 8100 wont just boot

My Toshiba Tecra 8100 completely fails to boot. It does not even reach
the Toshiba splash screen. There is some activity namely the HDD led
comes on briefy and you can here the CD rom power up but then HDD led
goes out and computer on led remains on with no further activity.
Pressing the reset button just repeats the whole process.
Pressing and holding power button for 5 secs does power down the
machine.
Pressing power button with F12 depressed sometimes gets to the upgrade
BIOS screen but sometimes the screen is garbled with random characters.