Re: How can I check if my hard disk is failing?
If it's a S.M.A.R.T drive then there are some applications which help you keep an eye on HD health.
As for not been able to boot some time, it could be for many reasons. From loose connection to corrupt memory locations in the RAM. Also try avoiding turning your laptop on below zero degree C, since although the harddisk surface itself is in closed environment, but the connections are not. And condensation may demage those fine connections.