In regards to your first question, that will bump the process priority of background tasks so that they might preempt your normal sort of app, like say a word processor. It's a setting meant more for systems that might do server duty where you want to give background tasks a higher priority. So, it's more likely to make your system slower rather than faster.
As for the second question, that can be typical for a laptop. A lot of heat is generated by the electronics, and that heat has to go somewhere. Laptops generally don't have a lot of room for heat dissipation like a desktop does, so it's much more important to be proactive about bleeding off heat.
It could also be a sign of spyware and other such garbage. Simple fact of life is that it's just not safe to use Internet Explorer as your main web browser. While maybe not the most common story around, there is the story of some guy who's system was hijacked by a bunch of spyware and the end result is that he now has to register as a sex offender. Look to switching to Mozilla or Opera as soon as you possibly can, and remember that not using IE means not using Outlook Express as well, and adding Windows Media Player to the list might not be a bad idea either. There are plenty of free replacements to be had if you look, many much better. You'd be wise to start searching immediately.
Recently, I believe a change a setting regarding CPU, which is 1.8 Ghz, on a Windows XP notebook. The steps are:
1. right click "My Computer"
2. click "Properties"
3. click the "Advanced" tab
4. under "Performance", click "Settings"
5. click the "Advanced" tab
6. under something "CPU priority" (I think), or the first box, click "Background Service"
7. click "OK" until you get out of the dialog boxes
I wonder if this setting can really speed up the computer. Also, I find that my CPU fan starts to run furiously, even if my computer is idle. Is there something wrong? I would like to hear some ideas.