Most likely, you need to change boot order in BIOS.
Watch your computer screen, when computer starts, and while the screen is still black, you'll see at the bottom something like:
Press "some key" to enter setup
When you press that "some key", it'll bring you to BIOS.
Make sure, the boot order reads:
- floppy
- CD drive
- hard drive
Save changes, and exit.
Put Windows CD in, and restart computer.
Watch the screen. At some point, the screen will say:
Press "some key" to boot from CD
Press that "some key", and you should be on your way to reinstall Windows.
