For those who can't get past lvl 7 (I can't with alt either, but had found a different way before consulting the guide), you can also just hold you mouse button all the way, then you can cross the walls or just hold the mouse button and take the cursor out of the screen, to drag it in again when the end is nearing. Be sure to release the mouse over the finish!
I was figured a way out of each lvl but 10 (oh yeah and 5, had the idea but mistimed or so), but I did not read anything new here as I had figured out the ctr-mouse thingie already. Even with the ctrl-thing I was unable to finish the lvl, though and I did not feel it would be the cheating enough for this game. I did figure a way - moving out of the window really fast (yes, it's possible in 10) and then alt-tabbing with the mouse in place already. However, there was a check where such large jumps were not allowed. What I did then was use x-master-nl's comment and stretched it a bit as I also use task manager on always on top, but I dragged Task Manager around, so I would never make big jumps, just small ones.