High-quality PC audio is important to me, as I spend a lot of time listening to music on my desktop. In previous columns I've discussed the aural advantages of lossless audio codecs (like FLAC), discrete sound cards, and specialty music player software. Alas, even with all of those tools installed and properly configured, it is possible to suffer less-than-optimal sound on a Windows XP-based PC, as the operating system has a tendency to muck with music without your consent. Happily, a free, easy-to-use program, called ASIO4ALL, addresses this annoying Windows habit. (I'm told that the app can improve sound on Vista PCs, too, but I have not tested that claim.)

So how does XP interfere with your music? Simply put, the OS hands off audio chores to a piece of software called the Kernel Audio Mixer, or Kmixer, which automatically resamples audio files--oftentimes rather poorly--creating output that differs from the original recording. The effect is typically pretty subtle, and if you are listening to low-bit-rate MP3s you probably won't notice it.

However, if you're like me and you listen to lossless audio because you prefer to hear music the way the artist recorded it, you can use ASIO4ALL to do an end run around Kmixer, sending an unadulterated version of the audio right to your sound card. Musicians who record using PC hardware have long used ASIO, which stands for Audio Stream Input Output. Mid- to pro-level hardware may include drivers with ASIO support, but lower-end hardware--such as integrated motherboard audio chips and some basic sound cards--tend not to. So an enterprising gentleman named Michael Tippach created ASIO4ALL. He says the original goal was to address the latency issues that Kmixer introduced into the audio recording process. It was only later that audiophiles started using it to achieve better audio from their PCs.

To use ASIO4ALL, you'll need a compatible media player, such as foobar2000 or WinAmp (Windows Media Player and iTunes don't support it). I recommend installing foobar2000. You also need to download the foobar2000 ASIO DLL (click on the Optional Components link on the foobar2000 site); the DLL file should go into foobar2000's Components folder on your hard drive.

Next, download and install ASIO4ALL itself. Launch it by clicking on its Off-line Settings option in the Start menu. You should see your computer's audio device highlighted; if you have more than one, select the one you intend to use.

Now launch foobar2000. Navigate to File, Preferences, and choose Output. In the resulting dialog box, select Output (under Playback), and then ASIO Virtual Devices, before clicking the Add New button. A new dialog box should appear with your audio device and various mapping coordinates (left, right, and so on) listed. Select one, then click OK, Save All, and Close.

Return to your music collection, fire up your favorite reference (highest quality or original recording) tunes, and start listening. You should hear a noticeable improvement in audio quality with even the default (Simple) settings.

I'm confident you'll get better audio through ASIO4ALL. And remember: It doesn't change anything in your drivers, so if you're not happy with the results, you can simply stop using it.