CUCM has "Cisco OS" upgrades. (even though it's windows, it's Cisco OS"
For Unity though, it should have been installed with the Unity Platform Discs that use Windows 2003 as the base. (no "special" load like Cisco OS". If somehow someone loaded the Cisco OS for CUCM and used it for Unity, they should be slapped on the wrist and make them go back and reload it correctly. It's an unsupported by Cisco and huge issue for the customer.
You can load Unity (2) ways only. Cisco Platform Discs or load it manually with a Windows 2003 or 2000 disc from MSFT. Either way is supported.
As for the window patches, you can download the Cisco Unity Windows Update package. It will scan the system apply missing patches where needed for the Windows 2003, Exchange and SQL.
In CCO, under Unity 5.x, click the Windows updates package. It's about 300 megs and release monthly or every other month I believe.
I'm not able to access my old voice mail messages all of a sudden. The recording says something like 'the message is currently not available'. This has never happened before in all the years I have been using this system. I have t...