A couple other thoughts as well. Some sidebar apps are known to cause high cpu-usage at times. It would mean a bit more if you could get the task manager screenshot while it's at high-usage, too.
But yeah, definitely consider switching the antivirus software. It seems like all the subscription ones bog down your machine more than they should. I used to use AVG free edition, but one update a year or so ago cause it to go nuts. Switched to Avast, and couldn't be happier. works like a charm, and doesn't eat my cpu.
Also, have you ever cleaned out your startup items? If not, run 'msconfig' and go to the startup tab. There's probably lots of stuff on there that you don't really need to be running right off the bat. Cleaning that out can do wonders for improving startup speed, and also kill off some unnecessary ram and cpu usage.
Final thought... I'm kinda alarmed by the high memory usage by firefox. either you've got tons of windows open, or firefox uses more memory that I would think it should. I'm running Chrome, and it only uses about 30k, not 130k.