Is it ok to have more than one antivirus installed?
No. We highly recommend that only one antivirus program be installed on your computer. If you're dissatisfied with the antivirus program you currently have installed we suggest that it be uninstalled, and a new antivirus program installed. Having more than one antivirus on the computer can cause a number of different issues. Often the most common issue being a confliction between the different antivirus programs causing your computer to become unprotected.
Although we only recommend one antivirus program on the computer, it's more than acceptable to have one ore more spyware or malware protection programs on the computer in addition to an antivirus scanner.