When you install the Symantec Endpoint Protection (SEP) client, the installation fails with MSI error 1500, indicating that another installation is in progress.
Error 1500. Another installation is in progress. You must complete that installation before continuing this one.
The MSI installer checks to ensure that only one program can install on the computer at a time. This error means that one of two conditions exist:
To troubleshoot this issue, try each of the following solutions until the problem is resolved:
Perform a clean boot of Windows (Microsoft Knowledge Base link) and install SEP.
Use System Restore to return the computer to a previous state, and install SEP.
Re-image the computer from a known good state, and install SEP.