The problem with Windows 98 isn't really cpu usage. I have run 9x at 100% cpu for 3 years straight...from boot-up to shutdown, running like that for days or even weeks at a time. (probably longer, but I didn't really pay attention to it before 3 years ago).
The 2 things that are the problem with windows 95/98/ME is RAM and user/GDI resources.
No matter how much RAM you have, 9x will eat it all, want more, and slow down. I have found it actually behaves better if you have less ram....better, but slower.
The biggest problem is the user/GDI resources. If you have ever run the little resource meter that comes with 9x and let it sit in your tray, you would know what I was talking about.
It starts off nice & green when you boot up and the more things you run, the lower the level of green goes...then it turns yellow...then it turns red and you get a low resource warning. The only thing you can do when you get that warning is start closing things in a hurry till you get back to green again. If you don't, you will end up with windows freezing on you and you will have to hit the reset.
Sometimes closing just about everything you have open isn't enough and the green doesn't return and you have to reboot to get things back to normal. This is just the way 9x is and there isn't much you can do to get the green back once this happens, if it doesn't want to play nice.
What makes this go red?
Every window you have open uses resources. Every picture on your screen uses resources...every icon, every sound, every open file, screensavers, wallpaper, installed fonts, etc.
if you want to make the problem less, you have to use less.
1. Don't use desktop wallpaper.
2. Don't display desktop icons. use the start menu.
3. In Explorer (My Computer) use list view or show details instead of using icon view or thumbnails.
4. Do not install fonts you do not need to use on a regular basis. If you want to use a special font for something, you can keep it in a folder and click to open it and minimize it. As long as it is open, it will appear in your font list in the program you are using. Then close it when you are done.
5. Do not use a screensaver...turn your monitor off when not in use, instead...or use power management to turn it off for you. (you will save money on electricity and extend the life of your monitor too)
6. Try not to have many windows open at the same time...especially browser windows. Try to use a browser with tabs if you can, and keep the tabs to a minimum.
7. Try to run simple programs that do one thing...only what you need them for. It is better to use Notepad to make a .txt file than MS Word. Better to use Windows Picture Viewer to just look at an image than Photoshop.
8. Reduce the number of programs that load at startup. If you will not be using Quicktime or RealPlayer, they don't need to load at startup and be sitting in your tray and waste valuable resources.
9. Do regular spyware and virus scans...this kind of garbage that sneaks onto your pc can ruin your day by stealing all your pc's resources...and other even worse things.
10. And if you need to do many things at once that are similar, then get a program that will do all of them combined. Like instead of running AIM, Yahoo, MSN, ICQ, IRC, etc all at the same time..use a program like Trillian that can access them all at the same time. 1 program that does the work of many and uses less resources to do it than running them all. (DON'T use GAIM...it uses GTK and GTK does NOT play well with 9x and will cause any software with an IE based browser object to crash...except IE
11. Experiment with different software. Some software that does the same thing can be better than another. Like your antivirus. Norton's & McAfee use a lot of resources to keep you safe. AVG will keep you safe and use less. The same is true with other software too.
Most of all, be observant. Your pc is your friend and will tell you when it doesn't like something or when you are doing something wrong before you get an error...you just have to pay attention for the little things and respond kindly with what will make your pc happy.
This page has a good explanation of the user/GDI problem if you want a simple technical explanation: http://www2.whidbey.com/djdenham/Window_memory.htm