Suggested Solutions
The following suggestions come from Gary McTaggart and Erik Johnson at Valve, and from users in various forum posts. While some of these suggestions have improved the situation for some people, none of these suggestions eliminate the problem entirely.
From Valve: Set snd_async_fullyasync to 1 in the console or config file.
From Valve: Lower in-game texture detail and/or sound detail.
Set the -heapsize launch option to half your total RAM. For example, if you have 1 GB of RAM, add the launch option -heapsize 512000. People have also tried other values with limited sucess.
Run dxdiag and lower sound hardware acceleration.
If you are running the 5.1 or 4 speaker settings in Half-Life 2, change the setting to 2 speakers.
Set the snd_mixahead option to various values (0.4, 0.5, 1, 0).
Set cl_forcepreload to 1 and sv_forcepreload to 1.
Set cl_smooth to 0.
Defragment your hard drive.
Diable virus protection applications.
Increase AGP aperture setting in your motherboard's BIOS.
Use ffdshow to disable third-party MP3 CODECs.
Uninstall various third-party CODEC packs.
Remove Half-Life 2 completely and redownload or reinstall it.
To prevent auto-saving, mark the following files as read-only in the hl2\SAVE folder: autosave01.sav, autosave01.tga, autosave.sav, autosave.tga.
Install Omegadrive's modified drivers (Omega Drivers) for NVIDIA and ATI video cards.