I was about to publish my question asking why my pc will only boot in safe mode, when it eventually booted up. My pc took about 1,30min to boot up! why does it boot so long? It was fine yesterday!
There might be hints in Windows event viewer, like i/o-errors or timeouts. You might want to run the error check on your harddrive: right click on c in explorer, goto properties / tools. It needs a reboot on c.