Physically accessing the hard disk drive on the Toshiba Tecra 800 is a simple process.
Turn the machine off, and unplug the power supply.
There is a long cover plate on the left hand side of the machine that surrounds the power button, and covers the hard disk drive assembly.
To remove the cover turn the machine over and locate the (Phillips head) screw that holds this cover in place; remove the screw, and gently remove the cover.
The hard disk drive may then be removed from the machine, and replaced.
Assembly is simply the reverse procedure.
Be sure to use a replacement hard disk of the same class.
The replacement hard disk will of course require formatting, and the installation of an operating system and software as appropriate.
Caution: Treat both the machine and the hard disk drive assembly with care; both can be damaged by poor physical handling, and electrostatic damage.
Hope that assists.
PS. If you are interested in complete disassembly illustrations for this unit, refer to the Toshiba FRU (Field Replacement Unit) Service Manual for the Toshiba Tecra 8000 series of notebooks.