Fix

In some cases this issue can be resolved by recreating your iTunes media library. This can be accomplished via the following process:

1. Quit iTunes if it is open
2. Navigate to the following directory: \Documents and
   Settings\username\My Documents\My Music\
3. Open the iTunes folder
4. Remove the following files: iTunes Music Library.xml and iTunes Library.itl. Put them in another location on your hard drive for safe-keeping.
5. Launch iTunes and navigate to the "File" menu then select "Import." Find the file iTunes Music Library.xml from the previous step and click "Choose."
6. Failing the above, quit iTunes and navigate to \Documents and Settings\username\My Documents\My Music\ and delete all files in the "iTunes" folder. Next, launch iTunes again and re-select "Import" from the "File" menu. Locate and re-import all of your music and other media.

Fix

This problem can often be fixed by reinstalling the latest version of QuickTime via the following steps:

1. Download the latest edition of QuickTime for Windows (make sure to pick the option without iTunes)
2. Choose to save the file to your disk, then double-click the .exe file and install QuickTime
3. After QuickTime is successfully installed, download iTunes again, choosing to save the file. Double-click the iTunes installer .exe and proceed with installation.

Other potential fixes for this issue include:

Run a disk check Disk errors, particularly in Windows XP, can prevent proper iTunes installation. See this Microsoft Knowledge Base article for instructions on performing a disk check/repair.

Use Windows Installer Cleanup Use the Windows Installer Cleanup tool to remove any references to Apple-related installation files (QuickTime, iTunes, etc.), then re-try using the aforementioned two-step method to reinstall QuickTime and iTunes.

Feedback? info@windowsfixup.com.

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 your antivirus software package and exclude iTunes and the iTunes library (located in C:\Documents and Settings\yourusername\My Documents\My Music\iTunes) from the scanning routine. Because some iTunes library files are updated every several seconds, constant scanning by antivirus software can cause a massive slowdown.

Check for conflicts Use the instructions in this Apple Knowledge Base document to check for potential conflicts with iTunes. The suggested process involves using MSCONFIG to disable startup or system services that could be causing a slowdown, then re-enabling services one by one or in groups to check for recurrence of the conflict.

Add iTunes to firewall exceptions If you are experiencing particular slowness when accessing the iTunes store, try adding iTunes to the exception list in your Windows firewall. Instructions for doing so in Windows Vista are here, and instructions for Windows XP here.

You may also want to check any third-party firewall software and add iTunes to its exceptions list.
Turn off Genius It appears that that the iTunes Genius feature can cause slowness for some users. Try turning the feature off from the “Store” menu.

Update to the latest version Make sure you are using the latest version of iTunes, available from Apple’s Web site.