I have a single headset that I use constantly. My computer output jack is in an awkward location, so I've set up a simple audio splitter. One side is plugged in to my headset, the other side is plugged into an audio cable extender which I leave on my desk for when I want to use speakers etc. The headset also has a mic and output cable. The output side of the headset is plugged directly into the computer's input jack. See artful diagram below.

As far as I can tell, all should be working great - except it isn't. I constantly get the little popups from windows 7 saying "You just unplugged/plugged a device from/into the audio jack". This is incredibly annoying. Any ideas?