I'm using Windows Media Player 11, with all updates. Anytime I play a
music file, MP3, WAV, AU, etc, it plays for exactly 10 seconds, then
the playback pauses and Internet Explorer launches to this URL:

www.flashcodec.com

Then the browser window closes and another window opens to ask if I
want to download/open/run this file:

Windows_Media_Player_Flash_Codec_Plugin.exe

I saved the EXE and scanned it, and sure enough, it contains a virus.

What I can't figure out, is what is causing this behavior. Also, it
only happens on one user account. I'm using XP SP2, and I have 2
admin user accounts, and 1 doesn't have this issue, and the other
does... so it must be some per-user setting. I don't see any weird
processes running, and my anti-virus software isn't reporting anything
(unless I download and run/scan that EXE).

Also, if I skip past the 10 second mark in the song (click the slider
bar to jump to 11 seconds) then I don't have any problems, until the
next song plays, or I replay the song and it hits 10 seconds again...
so this virus must trigger to do something at exactly 10 seconds.

With all of the details I know about it, I can't believe I couldn't
find anything with my various searching (Google, etc). Anyone know
what it is?

I even installed Windows Defender, and no luck. I guess I'll try a
few other anti-spy-ware and anti-virus programs, but I've already
tried several with no luck... and usually Avast! finds everything.