OSX Lion stuck at reinstallation

Hello dear Apple community,

I recently decided to have a fresh re-installation of OSX Lion on my Macbook Pro because it was craaawling slow over the last few weeks.
I erased the hard disk and chose to re-install as indicated in the official apple assistance page.

The problem now, is that since yesterday (it's been more than 12 hours) my laptop is stuck at a white screen with a wheel spinning on the botton and a "forbidden" sign in the middle of the screen. Please see the snapshot below. It's been like that for more than 12 hours, and I thought I should wait for it to finish something that it has been doing, but watching a few videos and visiting some websites on how to re-install I saw that this shouldn't happen!

Note: Please, don't tell me what I should have done, like reinstalling from a flash drive etc. Please tell me, how I would be able to solve this now, because I need my computer to be functioning tomorrow morning for my job.
Thank you.