Symantec Antivirus Corporate version 10

I have the CD for the software. It was installed on a computer. The software’s autoprotect feature becomes disabled constantly. The software is reinstalled using the same CD. When installation completes, auto protect is still disabled, liveupdate does not work, and there is not an entry for it in the add/remove applet. The OS is WinXP Home SP2. Does anyone have an idea why this happens?