Honestly, it could be anything.
Have you installed anything recently that puts something in the task bar?
It's time you take a look at everything running and starting up when your computer does.
I would recommend using Autoruns
Not sure what all those things are? Go to HERE
for help with identifying those pesky startup items.
You should be able to figure out what it is that is starting up and causing the icon to come up.
You can also within Autoruns save the information to a file and post it to a location, such as skydrive, and I can take a look and see if I can isolate what it might be.
If you need help saving the log file, let me know and I can post steps.