All the Cisco CallManager versions 4.x and earlier run on the Cisco IP Telephony (IPT) operating system, which is the Cisco version of the Windows 2000 build. Therefore, in order to obtain the 2007 DST changes required for the operating system, apply either of these versions, which are available from Cisco Downloads
Certain Software Downloads/Upgrades from Cisco requires Additional access/Valid Service contract. Availing this contract would gives you access to most of the tools and to the Encrypted Software's.