Chrissie, try this:
Take the CD out of the drive.
Reboot the computer.
Load the CD again & restart the game. If that works then you can continue with the game. If not:
Take the CD out
Go to your C drive and clean out all temp. files, etc.
When done with that make sure all background programs are down, antivirus, screensaver, etc. etc.
Try restarting the game. Hopefully it will run now. If not we will have to dig deeper.
Its one of those doors that needs a thingy thing.