The Cisco IOS Software Releases 12.4 T has been retired and is no longer supported.
End-of-Support Date: 2016-01-31
Cisco's End-of-Life Policy
You can view a listing of available Networking Software (IOS & NX-OS) offerings that best meet your specific needs
If you want support information for the Cisco IOS Software Releases 12.4 T documentation, it may be available through Cisco.com Search or in the Cisco Community