If you are not using an external mixing board, this problem can be eliminated by adjusting the Windows 95/98 Volume Control. Quick on the Start button | Programs
| Applications | Multimedia | Volume Control. Next click on the Options menu and select Properties. Click on Adjust Volume for Recording and click OK. Remove the
check marks from any Select boxes you are not using. If you are recording microphone input, leave only the Mic Select box checked. (Some sound cards have their
own proprietary mixer which may look different that described here)

If this your sound card does not use a software mixer such as described above, or those steps do not help, consult the card's manufacturer for further advice.

If you are using an external mixing board, check your signal path to make sure you're not routing audio playback back into the sound card.