If you install Windows on top of itself, it should not erase any data. You will have to reinstall many of your programs. You will also have to redo any Windows settings, etc. But your pictures and stuff should be fine. Just make sure you do NOT format the drive, that would erase everything on it.

You should first try to back up important data though, if you can.

If you find the correct CD / DVD it should boot up automatically. You might have to go into the BIOS and set the CD / DVD drive as your first boot drive, though.