Thanks for your comments, BlackSheepNY.
I have 1.25 GB Ram on my Dell. And yes, it is a old computer. circa 2005. But I don't have a lot of unused programs on my machine any more.
I check my cpu usage and processes with the Windows Task Manager.
One of the processes that I noticed (with Firefox) is plugin-container.exe. This is used by Firefox to control the use of plugins so that if the plugin crashes, it will not cause Firefox to crash. I see this in heavy use on my XP computer when I run Radio Loyalty -- probably because of the multiple video ads. It frequently is using 80-90+ cpu.
There are some articles online about this process and even Firefox has some suggestions on how to modify my plugins to reduce the overuse of CPU. Suspect that while it might solve the high CPU usage, it may cause other problems. (ie not being able to see any video ads).
I am concerned that if I run my PC consistently at 90%+cpu, I may end up damaging it so that it won't work at all.
Ahhhhh, yes, "plug-in container." This one has been a wild hair for me, too (I also use Firefox). I've read all I can about plug-in container and have tried all I can try. Unfortunately, nothing has worked. Is your Firefox actually crashing when plug-in container goes crazy? You can enable "Crash Reporting" to Firefox so they get a report each time your browser crashes.
Click: Tools, Options, Advanced - Under "Advanced" are other tabs, choose "Data Choices" and then under "Crash Reporter" click "Enable Crash Reporter."
Firefox just recently updated once again - it's now Version 21.0. Make sure you have the most updated version. To do this, click on "Help," "About Firefox," and update from there if you don't have version 21.0.
Do you use Add-Ons and Plug-Ins? If so, click on "Tools," then "Add-Ons" then on the upper right hand side of the page, click the icon that looks like a GEAR and click CHECK FOR UPDATES. If there are any updates to your Add-Ons, it will be apparent on the LEFT hand side of the page where you will see the words "Available Updates" and a number next to that indicating how many of your Add-Ons have updates. Click it, and update those Add-Ons.
For Plug-Ins, again click on the word "Plugins" on the left hand side of the page. At the top of that page, you will see a link that says, "Check to see if your plugins are up to date." Click that link and it will open a new page to check all of your installed plugins. If there are any on that page that tell you you need an update, update them ASAP because when these plugins are not running the most recent versions, they can be a real pain and leave your computer vulnerable to other problems. Most of the plugin updates will need to be downloaded and installed, but don't neglect updating them - it could be a reason why you're having problems.