1. A firewall is a highly recommended. http://www.zonealarm.com”>ZoneAlarm< may fit your needs. I would also recommend entering passwords and other credentials on websites with https:// as part of the address. This means that the information is encrypted between your computer and the destination. However, still be aware that criminals can create eerily similar websites using https and steal your identity. Take a look at http://www.google.com/search?q=phishing&btnG=Search”>phishing and this will inform you of the threats that are out there.
2. I have not seen problems with McAfee updates due to conflicts with other programs. I am not familiar with these applications. The problems could be caused if there is a conflicting application port in use on the computer and one of these packages uses that port before McAfee can take it for its own use. I would suggest posting a question on the McAfee support forums and provide as much detail including system logs and other information about your system.
3. Total security is a myth. The best security is to never get online and expose the system to the threats that are out there. However, you can mitigate some of the threats by going with some of the standard offerings of packaging individual products both free & paid, or by going with something like the Norton or McAfee security suites. Sometimes your internet provider may provide these applications with your subscription or for a small fee. This way you can get support for your use.]
You have to make sure that a full, latest, and updated antivirus software is installed in your computer system. In addition, avoid opening files and webpages which are unfamiliar to you. Avoid clicking suspicious links and advertisements.