Trying to restore my iphone 4 and I keep getting unknown error 21 and then it stops?

Hello sdavies26,

Thank you for using Apple Support Communities.

For more information, take a look at:

Resolve iOS update and restore errors in iTunes

http://support.apple.com/kb/ts1275

Resolve specific iTunes update and restore errors

http://support.apple.com/kb/ts3694#10

Check for hardware issues

Try to restore your iOS device two more times while connected with a cable, computer, and network you know are good. Also, confirm your security software and settings are allowing communication between your device and update servers. If you still see the alert when you update or restore, contact Apple support.

Common errors: 1, 10-47, 1002, 1011, 1012, 1014, 1000-1020.

Have a nice day,

Mario