if ctrl+alt+delete does nothing and the caps lock (or num lock) lights don't respond either then it really has fully locked up.
Had anything changed when it started happening, such as anything new was installed or plugged in to the laptop?
The first thing I would do is goto HP's website and download all the drivers for the laptop and reinstall them all so you have the latest drivers for everything. if that doesn't cure it then I'd next try a system restore (I don't recommend that often!) and if still no joy then it's going to be restore it back to factory settings
if still no luck then it is a hardware problem, but as it's got windows 7 on it I assume it's new so don't even bother looking into hardware problems, just call HP, they have one of the best customer services departments in the world when it comes to warranty stuff in my experience.