This was an annoyance for me because I use AutoPlay for some things, but didn't want it popping up for magicjack. My solution just fools Windows into thinking the drive has content it doesn't, and uses that rule.
1) Before starting MJ there are two drives listed in My Computer, open the one that's not called a CD Drive. If you see a file called "DONT USE THIS DRIVE", you've got the right one.
2) Holding down SHIFT, right-click on the autorun file. Select "Open with..." and then choose Notepad in the new window.
3) Go the section labeled "[Content]". My solution was that because I want to use Autoplay for pictures but not music, I set MusicFiles=1. Save and close the file.
4) Eject the device from the taskbar, remove, and then plug in again. This makes sure the change was set.
5) Now just choose from AutoPlay options (Audio files in this case) and set the value to "Take no action"
Note that you can also set Software and Games to "Install or run program from your media" and then MJ will start automatically, but I prefer to start manually.
Disable AutoPlay popup in Windows 7
Moderators: Bill Smith, Pilot