Please follow the steps in the link below, exactly, after starting in "Safe Mode with Networking".

“Expand” the post titled: "Please try this" at the link below:
http://www.cnet.com/forums/post/f742c795-5881-433b-a29b-6d758efe5cd3/

And if you can't login to your normal user account from Safe Mode, try logging in to the hidden administrator, assuming you've enabled it. If you haven't, then enable it from a command line in Safe Mode, like this:

Click on Start, (or press Windows Key+ R to open a "Run" line) then type: “cmd” in the Search line, then RIGHT click on “cmd.exe” at the top of the search page, choose “Run as administrator”.
At the command prompt, type: Net user administrator /active:yes
Press the “Enter” key..
An unpassworded Administrator account will now show up on the Welcome screen when you restart.


Hope this helps.

Grif