I keep getting the error message "There is no disk in the drive" when opening ITunes.

Does iTunes otherwise open normally after you acknowledge the error? If so there could be a preference file that isn't being updated when you close iTunes. Does it make any difference if you insert an audio CD before launching iTunes?

When you reinstalled iTunes did you do a complete tear down of all related components, such as is shown in the second box of Troubleshooting issues with iTunes for Windows updates?

tt2

For general advice see Troubleshooting issues with iTunes for Windows updates.

The steps in the second box are a guide to removing everything related to iTunes and then rebuilding it which is often a good starting point unless the symptoms indicate a more specific approach. Review the other boxes and the list of support documents further down the page in case one of them applies.

The further information area has direct links to the current and recent builds in case you have problems downloading, need to revert to an older version or want to try theiTunes for Windows (64-bit - for older video cards) release as a workaround for installation or performance issues, or compatibility with QuickTime or third party software.

Your library should be unaffected by these steps but there are also links to backup and recovery advice should it be needed.

tt2

My guess is that the preference file that records which library file iTunes should access has become corrupted. Press & hold down shift when starting iTunes. This should give you an option to choose or create an iTunes library. Click choose and browse to the location of your iTunes Library.itl file, normally inside <User's Music>\iTunes.

If that doesn't fix it see Fix unexpected quits or launch issues in iTunes for Windows and try the section marked user-specific issues.

tt2