If you have an iPad 1, the max iOS is 5.1.1. For newer iPads, the current iOS is 6.0.1. For the iPad Mini the iOS is 6.0.2. The Settings>General>Software Update only appears if you have iOS 5.0 or higher currently installed.
iOS 5: Updating your device to iOS 5 or Later
http://support.apple.com/kb/HT4972
How to install iOS 6
http://www.macworld.com/article/2010061/hands-on-with-ios-6-installation.html
iOS: How to update your iPhone, iPad, or iPod touch
http://support.apple.com/kb/HT4623
If you are currently running an iOS lower than 5.0, connect the iPad to the computer, open iTunes. Then select the iPad under the Devices heading on the left, click on the Summary tab and then click on Check for Update.
Tip - If connected to your computer, you may need to disable your firewall and anitvirus software temporarily. Then download and install the iOS update. Be sure and backup your iPad before the iOS update. After you update an iPad (except iPad 1) to iOS 6.x, the next update can be installed via wifi (i.e., not connected to your computer).
Update and restore alert messages on iPhone, iPad, and iPod touch
http://www.buybuyla.com/tech/view/012953a0d412000e.shtml
iOS: Resolving update and restore alert messages
http://support.apple.com/kb/TS1275
From above link.
Error 2, 4 (or -4), 6, 1000, 9006
- Follow Troubleshooting security software. Often, uninstalling third-party security software will resolve these errors.
- There may be third-party software that modifies your default packet size in Windows by inserting a TcpWindowSize entry into your registry. Your default packet size being set incorrectly can cause these errors. Contact the manufacturer of the software that installed the packet size modification for assistance or follow this article by Microsoft: How to reset Internet Protocol (TCP/IP).
- Verify that access to ports 80 and 443 are allowed on your network.
- Verify that communication to albert.apple.com or photos.apple.com is not blocked by a firewall, or other Internet security setting.
- Discard the .ipsw file, open iTunes and attempt to download the update again. See the steps under Advanced Steps > Rename, move, or delete the iOS software file (.ipsw) below for file locations.
- Restore your device while connected to a different network.
- Restore using a different computer.
iPad: Unable to update or restore
http://support.apple.com/kb/ht4097
Cheers, Tom 😉
Message was edited by: Texas Mac Man