Sometimes if the Mic Boost is enabled it might give such distortions.
1. Click on Start - Programs - Accessories - Entertainment - Volume Control
2. Click on Options Properties - Choose Recording - Click Ok
3. Under Microphone - Click on Advanced and uncheck the mic boost options.
This might help in some cases.
Jim Coates -- senior forum member
jimco wrote:fox,To install the generic Intel driver without uninstalling SigmaTel :> Go to Start/Control Panel/System/ Hardware tab, then click on Device Manager. Go down to Sound, Video, and Game controllers and right click on SigmaTel. Choose properties. > Go to the Driver tab and click on Update Driver. > Answer "No" to the Windows Update question. > Choose "Install From List or specific location". > Hit next and then choose "Don't Search, I will choose driver I want to install". > You will get a list of Sigmatel drivers. Uncheck the box that says "show compatible hardware". > Select Intel, and then select "Intel AC 97 Audio Controller". XP replaces the SigmaTel driver with the Intel AC97. > To reinstall the SigmaTel just select "Rollback Driver".