New media (videos, music, etc.) cannot be added to iTunes

Several users have reported a problem in which various media, including video, music and podcasts cannot be added to the iTunes library under various versions of Windows.
Fix
In some cases this issue can be resolved by recreating your iTunes media library. This can be accomplished via the following process:

Quit iTunes if it is open
Navigate to the [...]

iTunes 8.1.1 Released; Fails to Install: Fix

A number of users have experienced problems updating to the newly released iTunes 8.1.1. Generally, when this issue occurs, installation appears to proceed normally but then delivers the error message “The installer encounted errors before iTunes could be configured. Your system has not been modified. To retry these operations at a later time please return [...]

Slow iTunes: Boosting Performance

A number of Windows iTunes users have reported extremely poor performance from the application. Symptoms include long lags when clicking on items, delays before playback starts, slow launches and more.
Fixes
There are a few specific fixes that can provide a significant boost in iTunes for Windows speed.
Exclude iTunes library from antivirus software Launch [...]