Apple has released iTunes 10.2.1 downloads to allow you to upgrade your device to iOS 4.3 [iphone 4 3GS ipod touch 4 3G ipad and Apple Tv 2G] . Download and update Itunes 10.2.1 directly to your computer by launching your existing iTunes application , going to top navigation bar and click on help and in the drop down menu select “Check for Updates” as shown in the image below .
The following window will pop up asking for confirmation to download and update iTunes 10.2.1 on your computer . Proceed by clicking “Download iTunes” .
You can also download a fresh installation setup on your computer from Apple.com here .
Useful Links : Download iOS 4.3 IPSW Files