Maximum screen resolution is 800x600

Go to the panel on the top of your desktop.
System -> Preferences -> Screen Resolution, then choose correct resolution that fits your screen and press "Apply" button.

it doesn't give me the option of any higher resolution than 800x600.

Is this http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?lang=en&cc=us&objectID=c00255308
 your model?
maybe your video driver is not correctly installed? Check System->Administration -> Hardware Drivers to see if there is proprietary driver for your video card.

Try this. Maybe it helps.

1: Copy the file /etc/X11/xorg.conf to /etc/X11/xorg.conf.bak
2: In a Terminal enter sudo gedit /etc/X11/xorg.conf
3 Change the screen section (the sub section is important)

Section "Screen"
 Identifier "Default Screen"
 Device "nVidia Corporation NV5M64 [RIVA TNT2 Model 64/Model 64 Pro]"
 Monitor "Generic Monitor"
 DefaultDepth 24
        SubSection "Display"
                   Modes "1280x800"
        EndSubSection
EndSection

4: Save the file
5: Restart the system

Hope it helps.
Peter

the video card is the Trident cyberblade 3d and I have not been able to find a driver download for it. The information I have on this card is
*-display UNCLAIMED
       description: VGA compatible controller
       product: CyberBlade i1
       vendor: Trident Microsystems
       physical id: 0
       bus info: pci@0000:01:00.0
       version: 6a
       width: 32 bits
       clock: 66MHz
       capabilities: agp agp-1.0 pm cap_list
       configuration: latency=64

Did you try?
Peter