Whether you're chasing your first Grammy, cutting deals over a VoIP phone, or dictating the next great American novel to your PC, the more accurately your system captures audio, the better you'll sound.
In many instances the sound processors built into PC motherboards provide adequate quality for VoIP calls, voice-recognition applications, and other audio uses. But audiophiles, musicians, and others who have discriminating ears will want the superior processing power and input quality offered by a high-quality sound card.
Windows' Sound Recorder app lets you test your on-board sound hardware and microphone: In XP click Start, All Programs, Accessories, Entertainment Sound Recorder, and in Vista click Start, All Programs, Accessories, Sound Recorder. Make a short recording of your voice or of other sounds, and then play it back. If you hear static, popping, or other unwanted noises, you may need to spring for a new microphone and/or sound card.
You don't need an internal sound card that plugs into a PCI slot. An external USB audio interface permits easier access to connectors, and you can move it between PCs in a jiffy. USB audio boxes range from Griffin Technologies' $40 iMic to Creative's $130 E-MU 0202. For me, Turtle Beach's $80 Audio Advantage SRM offers a great balance of performance and features for the price.
External audio boxes digitize analog signals that the microphone captures, before they enter the electrically noisy interior of the computer's case. This is especially important if you're recording sound through a laptop. If you're committed to using an internal sound card, Andrea Electronics' $50 USB Adapter digitizes the audio signals from your microphone or microphone preamp. Also, all USB microphones have analog-to-digital converters built in, which provides an alternative conversion method.
For VoIP, voice recognition programs, and other applications where ambient noise can interfere with sound quality, a headset or microphone with built-in noise-canceling is a worthwhile investment. Logitech's Premium USB Headset 350 uses a noise-canceling microphone.
Sound Windows Advice
To optimize sound hardware performance, go to the Web site of the company that made your PC, motherboard, or sound card and download the latest version of your Windows audio driver program. Make sure that Windows is running the latest version of DirectX, too: Click Start, Run (just Start in Vista), type dxdiag.exe, and press <Enter>. Your DirectX version will be listed under the System tab near the bottom of the screen. Browse to Microsoft Download Center: DirectX to download the latest version (9.0c for XP, 10 for Vista).
Windows XP's Sound Hardware Test wizard checks your microphone for proper configuration. Click Start, Control Panel, Sounds (Sounds, Speech, and Audio Devices in Category view)Sound and Audio Devices, Voice, Test hardware, and step through the wizard. In Vista, use the Microphone Setup wizard: Click Start, Control Panel, Ease of Access, Set up a microphone.
Fine-tune the balance setting of your PC's microphone via the slider control in its Properties dialog box.
Windows also provides useful volume controls and balance settings specifically for your microphone, line-in, and other input channels. In XP return to the Sound and Audio Devices Properties dialog box, select the Volume tab, and click Advanced under Device volume (for some higher-end audio products, the settings are listed under the Audio tab). Choose Options, Properties, and under 'Adjust volume for', select Recording. Choose the desired input channels, and click OK, and you'll see the Windows volume mixer panel. In Vista, click Start, Control Panel, Hardware and Sound In Categories view), Sound, and select the Recording tab. Double-click the desired channel and select the Levels tab. 
