Mozilla had some problems with one upgrade which may be affecting you.
Download your mozilla program, and reinstall it. The new version will overwrite any Mozilla problems.
Otherwise, tell us more about your computer, motherboard, and configuration.
I don't see any problems in the HiJackThis log, but I am no expert. What I do see is an install pattern that will contribute to slowness. You are using Zone Alarm, AVG, BigFix, and AVAST, along with some other stuff. You may have a case of overkill conflicts. I would remove either AVAST or AVG... and run one or the other, but not both. I would also remove BigFix, and ZoneAlarm.
Zone Alarm has been a lot of trouble now for several months. Comodo is also free and works much better.
Then I would run PC-Decrapifier after you remove what you can... or CCleaner... followed by a full defragment of the hard drive if you have not performed one recently.
It appears your computer is an eMachine. If so, that could be a problem if your computer is more than two years old. They have a tendency to slow down, more and more than suddenly quit from a failed motherboard.
