Kubuntu 10.04LTS. Desktop screen does not fill available area...

[Clive Chacksfield]

Have just installed Kubuntu 10.04LTS on an old Toshiba Tecra8200 in an 
effort to re-use an old laptop (previously running Windows XP Pro):

Processor: Intel Pentium III 1 GHz
Installed Memory: 256 MB (SDRAM) [Looking to increase this to 512MB soon]
Display: 14.1 in
Hard Drive: 20 GB

Installation went OK and runs OK (slowly, but as expected with only 
256MB RAM). Problem is, the desktop screen does not fit the available 
screen area. There's about a 3cm black border around the desktop.

Have gone into the BIOS settings, have changed the 'display setting: 
'LCD Display Stretch' to 'enabled'. Now, the BIOS screen fills the 
screen, problem solved, I thought.

Saved the changes to the system settings and confirmed this, but when 
the laptop reboots, the problem remains.

Went back into BIOS settings to check, but 'LCD Display Stretch' still 
shows as 'enabled'.

Any ideas?