You have not installed drivers
for your integrated graphics chip, as your display is listed as "Standard VGA Adapter"
Open Windows Update and check for updates to see whether you get any graphics drivers via Windows Update.
I searched on the internet and have found your computer's user manual from here: Documentation
In it, your graphics chipset is listed as Intel Extreme Graphics 2 and motherboard chipset as Intel 865 GV.
Unfortunately, there are no Windows Vista drivers and hence no Windows 7 drivers for your graphics card.
You may be able to get by if you install Windows XP drivers from here: Intel® 865 Chipset Family - Chipset information and downloads
Hope this helps!
Also, if this does not solve your problem, search the internet for your monitor's drivers as sometimes some resolutions and refresh rates may not be available unless you install your monitor's drivers.