years, I've used many utilities, fire walls and malware routines.
Many, and sadly they are well advertised and popular, can cause slow
downs, spontaneous program aborts, and internet blockages.
Peter Norton was a DOS genius! He could make DOS sit up and bark, but his company's Windows efforts were less than stellar. I'd been a loyal user for many years, but I finally jumped ship and would consider nothing that Symantec produces, now. I simply had too many problems with it.
McAfee is another product that can be intrusive and counter productive. Many people do use and rely on it, but it does NOT fill my needs and made my machines harder to manage and deal with. If it comes pre-installed, it gets the boot. It has made my life more difficult.
AVG is another product that I put in this category. I've never used it, but I've known many that have, and I've heard similar tales of woe that removal seems to eliminate.
None of these programs will simply go away. It usually takes removal tools to get rid of them. That, alone, disturbs me. If I put something on my machine, when I uninstall it, I expect it to be gone! Not with some products. Knowing this, alone, is sufficient for me to reject them.
Your mileage may vary, but this has been my experience.
There are many excelent programs that will fill basic security needs.
These are free or have free versions.
Fire wall: http://www.zonealarm.com/
Virus Protection: Avira Free
Virus Scanner: Clamwin Portable
Malware detection and removal Spybot - Free Version