I have downloaded CCM6.01a non bootable iso files UCSInstall_UCOS_188.8.131.520-4, which is available for download under our SASU contract.
Combined both the files and verified checksum. But am not sure how to start installation as this is non bootable image. May be I am being very stupid and missing to read some obvious documentation but any information about this is welcome
You will need a previous version of CUCM6 installed such as FCS version 184.108.40.2060-37.
There are no installable versions available from CCO. Talk with your local Cisco Partner or Cisco office to obtain the proper installation media.
If you have SASU or now ESW/UCSS, you should be able to order the upgrade (free) via Product Upgrade Tool (PUT). This will get you the latest shipping installation media as well as permanent license keys.