Yeah, thats why. The standard VGA drivers on earlier windows only produced 16 - 256 colours. You'll have to install Video Drivers.
Do you know what video card or chip you have in, or on your motherboard?
If you do, you'll simply need to download the driver for it again, and it'll sort itself out after installing
If not, download this program which displays exactly what is in your PC, and you can check what chip or card is running the video:
I hope this helps.