David,
Can you complete the steps in this document?
http://support.apple.com/kb/TS1567
Do you have any McAfee firewalls installed on your computer? Sometimes this actually stops or blocks AMDS, and if we can get into your settings we can allow AMDS so that it can be started.
If these steps don't help, it could be that AMDS isn't functioning properly. You can reinstall it by going into your Control Panel and opening Add or Remove Programs, and removing both AMDS and iTunes, and then reinstalling iTunes. Note that this won't cause any harm to your media or data stored within your iTunes library.
CG