How long is it locking up for bud? Are you leaving it for a bit to see if it recovers or just rebooting after a few mins?
Right click my computer and go to "manage"
In the event viewer go to windows logs, look through the application logs, if there are any serious errors thats where you'll find them.
The other thing to check is in control panel, go to system and security and go to the action center, check for solutions to unreported problems, that one picked up that i'd got a dodgy sata cable, its a big improvement on the old windows error checkers.
Best of luck with it.
One more thing to check to see if its totally locked is the caps lock or num lock key, if the lights go on and off when you're pressing them the machine hasnt totally locked up, if thats the case i'd give it a bit of time to see if it unsticks.
If you can find the hard drive diagnostic software for your drive I'd run that too, hirens boot cd comes with a fair few.