Apple has just released iTunes 10.2 for Mac and Windows. You can download iTunes 10.2 from Apple website, it will be required in order to update to iOS 4.3. Download link is as under:

http://www.apple.com/iTunes/download

What’s New in iTunes 10.2?

As per release notes:

• Sync with your iPhone, iPad, or iPod touch with iOS 4.3.
• Improved Home Sharing. Browse and play from your iTunes libraries with Home Sharing on any iPhone, iPad, or iPod touch with iOS 4.3.

Apple is set to release iOS 4.3 on March 11, along with iPad 2.