"Arny Krueger" wrote in message
...
It is quite possible that Virtualdub and Soundforge are decoding your
video
files using their own private codec libraries, while it is expected that
Windows Media Player would use the main shared system codec libraries.
...
One approach would be to try reinstalling any other audio playing or
editing
software including Virtualdub and SoundForge. They were probably installed
after the previous OS service pack was installed and may have beneficially
overlaid some of the codecs that came with your PC.

VirtualDub does not instal any codecs (shared or otherwise), and has no
private codec library. It uses the ACM (Audio Compression Manager) interface
to decode audio.