Here are some things you can buy/get to improve sound quality:

- Of course, your microphone may suck. Usually the small microphones that people get spec. for computer use are less than desirable. However very nice microphones aren't typically designed for computers and are also quite expensive, and probably not reasonable if you're just gonna be doing simple recordings of your voice or something. So, get a high quality microphone designed spec. for a computer.

- New sound card. This always can help, of course. If you have a nice sound card you can record in better quality. There aren't any particular brands I can think of, so it'd be smarter to just browse around yourself and see what suits you best.

- As for sound programs, the sound recorder that comes with Windows 98 is, to say the least, quite crappy. Personally I use a program called Cool Edit 96 (There is also Cool Edit 2000) which works much better than the default sound recorder. The shareware only allows a limited amount of features at one time, so if you want all at once you'll have to purchase it. Or just get a crack.

- Be aware of the program sndvol32.exe. You can use it to adjust sound levels, etc. Explore every option. There is a screen for playing sounds and a screen for recording, use both.