iTunes 10 for Windows: Update iTunes
You can manually check for updates to iTunes, or set iTunes to check for new versions automatically every week.
Here are ways to check for iTunes updates:
To manually check for new versions of iTunes, choose Help > Check for Updates.
To have iTunes automatically check for new versions every week, choose Edit > Preferences, click General, and make sure the “Check for new software updates automatically” is selected.
When automatic updating is turned on, iTunes checks for new updates weekly. It checks only after you have quit and restarted iTunes at least once during a seven-day period.