Tap the F8 (or F5) key continuously from the moment you use the 'On' Switch until you hear a 'Bleep'.
There after you will need to navigate using the 'Up, Down, Left and Right' Keys. You may need to wait a while while all the Basic Drivers load, then chose to open in Windows.
This may allow you to clear whatever glitch has occurred. There is an 'off' chance that they have been to a site of doubtful reputation! So it may make sense to Update and run your Anti Virus and Anti Malwear Suites.
If the same problem persists after this, come back and other will add their 2 ha'penth worth.