Windows 7 system reserved drive autorun popup
Solution 1:
I've experienced this symptom with some versions of the Tom Tom GPS desktop software. (I presume the problem is related to scanning for a Tom Tom being connected via USB.)
If you have a Tom Tom, try exiting the software. (You must turn it off in the system tray, not just close the window.)
If this solves the problem for you, make sure to use msconfig to disable the Tom Tom agent in your startup software. (It's not necessary in order to use the Tom Tom; it's only purpose is to autorun the software when you connect the device.)