Is it safe to apply sp4 and other MS hotfixes to UNity 4.0 servers?
This is all covered under the Compatibility Matrix:
You'll see the currently supported service packs and corresponding unity versions as well as this note near the bottom:
"Microsoft frequently provides updates for Windows 2000 Server, Exchange Server, SQL Server 2000 and MSDE 2000, Internet Explorer, and IIS. These updates (known by a variety of names, including security rollup patches, security updates, critical updates, patches, and hot fixes) are limited to changes that fix specific problems. They do not include general defect fixes or new functionality. All of these Microsoft updates are qualified by Cisco from the day that Microsoft releases them. We recommend that you evaluate Microsoft updates in accordance with your server-software-maintenance policy to determine when to update the Cisco Unity server. If your company does not have a policy, we recommend that these Microsoft updates be applied to the Cisco Unity server as they are released. Cisco TAC provides support for a Cisco Unity system on which such updates have been installed."