If you hard drive is over three years old, or 40GB or smaller, it is time to replace the computer. If you don't know what a "hard drive" is, and you still run Windows 98, trust me... your hard drive is ancient
I do not have a strong brand preference. Any brand, even the cheapest model you can get , is significantly faster and more capable than your current machine. Technology has advanced so much since 1999 that it's impossible to buy a poor performer.
Best deals are online. Look for "refurbished machines". Best selection comes from tigerdirect.com. Dell Outlet, Gateway and HP also have refurbished machines online. Do your homework.
Do you have data on your old machine that you want transferred to the machine? Contact me.