This was one of those occasions where 2-year old toddler, glass of water, and laptop should not have come together... My wife may or may have added to the problems by chaos the battery out of the computer immediately after water hit laptop but before turning it off.
Result is a laptop (running Windows Vista) that won't boot in normal mode. But it will run in safe mode. Running chkdsk (okay, I accept that might be a bit old-school) it seems there are problems on the hard drive - the volume bitmap is incorrect and there are problems with the file system, and I'm hoping I can fix them if I can boot up from a USB stick.
But here's the strange thing - when I try and boot from a Windows Vista installation (on a USB), after selecting the option to boot from USB stick, the computer displays for a long time a black screen saying 'loading Windows' and then, when it flicks to the light blue of the Windows start-up screen, power cuts and the computer switches off. [I've double-checked and the USB seems to work on another laptop]
The laptop doesn't seem hot at all, so I don't think it's to do with overheating. Might it be to do with power supply?