Stuck whilst updating

[WildfireS3]

I'm totally new to the whole mac thing, having used PCs for years. I updated my 15" Macbook pro this evening and it asked me to restart, which I did. now it's stuck on a white screen with a stop sign and the little whirling icon going round. It's also getting really hot.

Any advice.

Thanks!

 

[simsaladimbamba]

Mac doesn't boot
Resolve startup issues and perform disk maintenance with Disk Utility and fsck
Troubleshooting: My computer won't turn on​

 

[Fubar1977]

I just had a 2010 Mac mini do this to me after updating OS X and I let it spin for about 1/2 hour then got bored and shut it down.
It then started up just fine and has been running for days without a problem.
I don`t necessarily advise doing this but I didn`t seem to have any other option apart from leaving it spinning all night.